diff --git a/app/Http/Controllers/Api/Admin/Customer/Concerns/ManagesCustomerServices.php b/app/Http/Controllers/Api/Admin/Customer/Concerns/ManagesCustomerServices.php
index 24462ed..5611edf 100644
--- a/app/Http/Controllers/Api/Admin/Customer/Concerns/ManagesCustomerServices.php
+++ b/app/Http/Controllers/Api/Admin/Customer/Concerns/ManagesCustomerServices.php
@@ -14,13 +14,22 @@ trait ManagesCustomerServices
         return response()->json(['error' => false, 'data' => $this->serviceProvisioning->getServices($uuid)]);
     }
 
+    public function attachService(string $uuid, Request $request): JsonResponse
+    {
+        $data = $request->validate(['service_id' => 'required|integer|exists:services,id']);
+
+        $service = $this->serviceProvisioning->attachService($uuid, $data['service_id']);
+
+        return response()->json(['error' => false, 'message' => 'Đã gán dịch vụ cho khách hàng', 'data' => $service]);
+    }
+
     public function bulkDeleteServices(string $uuid, Request $request): JsonResponse
     {
         $data = $request->validate(['ids' => 'required|array|min:1', 'ids.*' => 'integer']);
 
         $deleted = $this->serviceProvisioning->bulkDeleteServices($uuid, $data['ids']);
 
-        return response()->json(['error' => false, 'message' => "Đã xoá {$deleted} dịch vụ", 'data' => ['deleted' => $deleted]]);
+        return response()->json(['error' => false, 'message' => "Đã gỡ {$deleted} dịch vụ khỏi khách hàng", 'data' => ['deleted' => $deleted]]);
     }
 
     public function updateService(string $uuid, int $serviceId, Request $request): JsonResponse
diff --git a/app/Http/Controllers/Api/Admin/Service/ServiceController.php b/app/Http/Controllers/Api/Admin/Service/ServiceController.php
index 1c7761b..ecd3ee0 100644
--- a/app/Http/Controllers/Api/Admin/Service/ServiceController.php
+++ b/app/Http/Controllers/Api/Admin/Service/ServiceController.php
@@ -5,14 +5,19 @@ namespace App\Http\Controllers\Api\Admin\Service;
 use App\Helpers\OrderHelper;
 use App\Http\Controllers\Controller;
 use App\Jobs\VirtualMachine\Provision\ResendVmCredentialsEmailJob;
+use App\Models\ActivityLog;
 use App\Models\DomainPricing;
 use App\Models\ModuleVmware;
 use App\Models\Service;
+use App\Services\Customer\CustomerServiceAssignment;
 use Illuminate\Http\JsonResponse;
 use Illuminate\Http\Request;
+use Illuminate\Support\Facades\DB;
 
 class ServiceController extends Controller
 {
+    public function __construct(private readonly CustomerServiceAssignment $assignment) {}
+
     public function index(Request $request): JsonResponse
     {
         $perPage = min((int) ($request->per_page ?? 15), 100);
@@ -21,7 +26,8 @@ class ServiceController extends Controller
             ->where(fn($q) => $q->whereNull('order_item_id')->orWhereNull('type')->orWhere('type', '!=', 'domain'))
             ->when($request->filter, fn($q, $v) => $q->where('server_name', 'like', "%{$v}%"))
             ->when($request->status,  fn($q, $v) => $q->where('status', $v))
-            ->when($request->customer_id, fn($q, $v) => $q->where('customer_id', $v));
+            ->when($request->customer_id, fn($q, $v) => $q->where('customer_id', $v))
+            ->when($request->boolean('unassigned'), fn($q) => $q->whereNull('customer_id'));
 
         $paginator = $query->latest()->paginate($perPage);
 
@@ -71,6 +77,12 @@ class ServiceController extends Controller
 
         ModuleVmware::resolveVirtualMachineIds([$service->vmware]);
 
+        $service->setAttribute('activity_logs', ActivityLog::where('subject_type', Service::class)
+            ->where('subject_id', $service->id)
+            ->latest('id')
+            ->limit(50)
+            ->get(['id', 'event', 'description', 'causer_type', 'causer_name', 'old_values', 'new_values', 'created_at']));
+
         return response()->json(['error' => false, 'data' => $service]);
     }
 
@@ -82,14 +94,17 @@ class ServiceController extends Controller
             'action' => 'required|in:activate,suspend,cancel,detach-customer',
         ]);
 
-        $updates = match ($data['action']) {
-            'activate' => ['status' => 'active', 'suspended_at' => null, 'cancelled_at' => null],
-            'suspend' => ['status' => 'suspended', 'suspended_at' => now()],
-            'cancel' => ['status' => 'cancelled', 'cancelled_at' => now()],
-            'detach-customer' => ['customer_id' => null],
-        };
+        if ($data['action'] === 'detach-customer') {
+            $updated = $this->detachCustomers($data['ids']);
+        } else {
+            $updates = match ($data['action']) {
+                'activate' => ['status' => 'active', 'suspended_at' => null, 'cancelled_at' => null],
+                'suspend' => ['status' => 'suspended', 'suspended_at' => now()],
+                'cancel' => ['status' => 'cancelled', 'cancelled_at' => now()],
+            };
 
-        $updated = Service::whereIn('id', $data['ids'])->update($updates);
+            $updated = Service::whereIn('id', $data['ids'])->update($updates);
+        }
 
         return response()->json([
             'error' => false,
@@ -100,12 +115,21 @@ class ServiceController extends Controller
 
     public function detachCustomer(int $id): JsonResponse
     {
-        $service = Service::findOrFail($id);
-        $service->update(['customer_id' => null]);
+        $this->detachCustomers([Service::findOrFail($id)->id]);
 
         return response()->json(['error' => false, 'message' => 'Đã gỡ khách hàng khỏi dịch vụ.']);
     }
 
+    private function detachCustomers(array $ids): int
+    {
+        return DB::transaction(function () use ($ids) {
+            $services = Service::with('customer')->whereIn('id', $ids)->whereNotNull('customer_id')->get();
+            $services->each(fn (Service $service) => $this->assignment->detach($service));
+
+            return $services->count();
+        });
+    }
+
     public function resendCredentials(int $id): JsonResponse
     {
         $service = Service::findOrFail($id);
diff --git a/app/Services/Customer/CustomerServiceAssignment.php b/app/Services/Customer/CustomerServiceAssignment.php
new file mode 100644
index 0000000..74711bf
--- /dev/null
+++ b/app/Services/Customer/CustomerServiceAssignment.php
@@ -0,0 +1,94 @@
+<?php
+
+namespace App\Services\Customer;
+
+use App\Models\Customer;
+use App\Models\Invoice;
+use App\Models\ModuleHostingAccount;
+use App\Models\ModuleVmware;
+use App\Models\Service;
+use App\Services\ActivityLogger;
+use App\Services\Order\ServiceOrderRecorder;
+use Illuminate\Support\Facades\DB;
+
+class CustomerServiceAssignment
+{
+    public function __construct(
+        private readonly ServiceOrderRecorder $orderRecorder,
+        private readonly ActivityLogger $activityLogger,
+    ) {}
+
+    public function attach(Service $service, Customer $customer): Service
+    {
+        abort_if($service->customer_id !== null, 422, 'Dịch vụ đang thuộc khách hàng khác, hãy gỡ trước khi gán.');
+
+        DB::transaction(function () use ($service, $customer) {
+            $service->fill(['customer_id' => $customer->id])->saveQuietly();
+            $this->syncModuleOwner($service, $customer->id);
+            $this->orderRecorder->ensureForService($service->refresh());
+        });
+
+        $this->activityLogger->log(
+            event: 'attached',
+            logName: 'Service',
+            description: "{$this->activityLogger->getCauserName()} gán dịch vụ #{$service->id} cho khách hàng {$customer->fullname} ({$customer->email})",
+            subject: $service,
+            newValues: [...$this->customerValues($customer), ...$this->orderValues($service)],
+        );
+
+        return $service;
+    }
+
+    public function detach(Service $service): void
+    {
+        $customer = $service->customer;
+        if (! $customer) {
+            return;
+        }
+
+        $orderValues = $this->orderValues($service);
+        $orderItemId = $service->order_item_id;
+
+        $service->fill(['customer_id' => null, 'order_item_id' => null, 'invoice_id' => null])->saveQuietly();
+        $this->syncModuleOwner($service, null);
+        Invoice::where('service_id', $service->id)->delete();
+        $this->orderRecorder->discardOrder($orderItemId);
+
+        $this->activityLogger->log(
+            event: 'detached',
+            logName: 'Service',
+            description: "{$this->activityLogger->getCauserName()} gỡ dịch vụ #{$service->id} khỏi khách hàng {$customer->fullname} ({$customer->email}), xoá đơn hàng/hoá đơn",
+            subject: $service,
+            oldValues: [...$this->customerValues($customer), ...$orderValues],
+        );
+    }
+
+    private function syncModuleOwner(Service $service, ?int $customerId): void
+    {
+        if ($service->vm_id) {
+            ModuleVmware::whereKey($service->vm_id)->update(['customer_id' => $customerId]);
+        }
+
+        ModuleHostingAccount::where('service_id', $service->id)->update(['customer_id' => $customerId]);
+    }
+
+    private function customerValues(Customer $customer): array
+    {
+        return array_filter([
+            'customer_id' => $customer->id,
+            'customer_uuid' => $customer->uuid,
+            'customer_name' => $customer->fullname,
+            'customer_email' => $customer->email,
+        ], fn ($value) => $value !== null);
+    }
+
+    private function orderValues(Service $service): array
+    {
+        $order = $service->orderItem?->order;
+
+        return array_filter([
+            'order_id' => $order?->id,
+            'order_num' => $order?->order_num,
+        ], fn ($value) => $value !== null);
+    }
+}
diff --git a/app/Services/Customer/CustomerServiceProvisioningService.php b/app/Services/Customer/CustomerServiceProvisioningService.php
index 3d39dfe..a7487d1 100644
--- a/app/Services/Customer/CustomerServiceProvisioningService.php
+++ b/app/Services/Customer/CustomerServiceProvisioningService.php
@@ -5,7 +5,6 @@ namespace App\Services\Customer;
 use App\Helpers\OrderHelper;
 use App\Mail\ServiceRenewalReminderMail;
 use App\Models\Customer;
-use App\Models\Invoice;
 use App\Models\ModuleVmware;
 use App\Models\Order;
 use App\Models\Product;
@@ -35,6 +34,7 @@ class CustomerServiceProvisioningService
         private readonly VmwareRepositoryInterface $vmwareRepository,
         private readonly ServiceRepositoryInterface $serviceRepository,
         private readonly ServiceOrderRecorder $orderRecorder,
+        private readonly CustomerServiceAssignment $assignment,
     ) {}
 
     public function getServices(string $uuid): Collection
@@ -55,6 +55,11 @@ class CustomerServiceProvisioningService
         return $services;
     }
 
+    public function attachService(string $uuid, int $serviceId): Service
+    {
+        return $this->assignment->attach(Service::findOrFail($serviceId), $this->resolveCustomer($uuid));
+    }
+
     public function bulkDeleteServices(string $uuid, array $ids): int
     {
         $customer = $this->resolveCustomer($uuid);
@@ -63,9 +68,7 @@ class CustomerServiceProvisioningService
             $services = Service::where('customer_id', $customer->id)->whereIn('id', $ids)->get();
 
             foreach ($services as $service) {
-                $service->delete();
-                Invoice::where('service_id', $service->id)->delete();
-                $this->orderRecorder->discardOrder($service->order_item_id);
+                $this->assignment->detach($service);
             }
 
             return $services->count();
diff --git a/routes/api/admin/customers.php b/routes/api/admin/customers.php
index bc2ce58..9e2c550 100644
--- a/routes/api/admin/customers.php
+++ b/routes/api/admin/customers.php
@@ -29,6 +29,7 @@ Route::prefix('customers')
         Route::post('{uuid}/add-total', 'addTotal')->middleware('perm:customer.edit');
         Route::get('{uuid}/services', 'getServices')->middleware('perm:customer.view');
         Route::post('{uuid}/services', 'createService')->middleware('perm:customer.edit');
+        Route::post('{uuid}/services/attach', 'attachService')->middleware('perm:customer.edit');
         Route::post('{uuid}/services/bulk-delete', 'bulkDeleteServices')->middleware(
             'perm:customer.edit',
         );
diff --git a/tests/Feature/Api/Admin/Customer/DeleteCustomerServiceOrdersTest.php b/tests/Feature/Api/Admin/Customer/DeleteCustomerServiceOrdersTest.php
index 27056e5..ca67f9c 100644
--- a/tests/Feature/Api/Admin/Customer/DeleteCustomerServiceOrdersTest.php
+++ b/tests/Feature/Api/Admin/Customer/DeleteCustomerServiceOrdersTest.php
@@ -45,7 +45,7 @@ class DeleteCustomerServiceOrdersTest extends TestCase
         return Service::where('server_name', $serverName)->firstOrFail();
     }
 
-    public function test_deleting_service_hides_its_order_and_invoices(): void
+    public function test_deleting_service_detaches_customer_and_hides_its_order_and_invoices(): void
     {
         $kept = $this->createService('kept.vn');
         $removed = $this->createService('removed.vn');
@@ -60,6 +60,54 @@ class DeleteCustomerServiceOrdersTest extends TestCase
         $this->assertSoftDeleted('invoices', ['order_id' => $removedOrderId]);
         $this->assertSame([$kept->orderItem->order_id], Order::pluck('id')->all());
         $this->assertSame(1, Invoice::count());
+
+        $removed->refresh();
+        $this->assertNull($removed->deleted_at);
+        $this->assertNull($removed->customer_id);
+        $this->assertNull($removed->order_item_id);
+
+        $log = $this->actingAs($this->admin, 'admin')
+            ->getJson("/api/v1/administrator/services/{$removed->id}")
+            ->assertOk()
+            ->json('data.activity_logs.0');
+        $this->assertSame('detached', $log['event']);
+        $this->assertSame($this->customer->email, $log['old_values']['customer_email']);
+        $this->assertSame($removedOrderId, $log['old_values']['order_id']);
+    }
+
+    public function test_detached_service_can_be_attached_to_another_customer(): void
+    {
+        $service = $this->createService('moved.vn');
+        $this->actingAs($this->admin, 'admin')->postJson(
+            "/api/v1/administrator/customers/{$this->customer->uuid}/services/bulk-delete",
+            ['ids' => [$service->id]],
+        )->assertOk();
+
+        $this->actingAs($this->admin, 'admin')
+            ->getJson('/api/v1/administrator/services?unassigned=1')
+            ->assertOk()
+            ->assertJsonPath('data.items.0.id', $service->id);
+
+        $other = Customer::factory()->create();
+        $this->actingAs($this->admin, 'admin')->postJson(
+            "/api/v1/administrator/customers/{$other->uuid}/services/attach",
+            ['service_id' => $service->id],
+        )->assertOk();
+
+        $service->refresh();
+        $this->assertSame($other->id, $service->customer_id);
+        $this->assertSame($other->id, $service->orderItem->order->customer_id);
+
+        $log = $this->actingAs($this->admin, 'admin')
+            ->getJson("/api/v1/administrator/services/{$service->id}")
+            ->json('data.activity_logs.0');
+        $this->assertSame('attached', $log['event']);
+        $this->assertSame($other->email, $log['new_values']['customer_email']);
+
+        $this->actingAs($this->admin, 'admin')->postJson(
+            "/api/v1/administrator/customers/{$this->customer->uuid}/services/attach",
+            ['service_id' => $service->id],
+        )->assertStatus(422);
     }
 
     public function test_recreating_same_service_discards_previous_order(): void