diff --git a/src/modules/auth/dto/request-otp.dto.ts b/src/modules/auth/dto/request-otp.dto.ts
index 83984af..4e40f10 100644
--- a/src/modules/auth/dto/request-otp.dto.ts
+++ b/src/modules/auth/dto/request-otp.dto.ts
@@ -1,5 +1,6 @@
 import { IsNotEmpty, IsString, IsMobilePhone } from 'class-validator';
 import { ApiProperty } from '@nestjs/swagger';
+import { Transform } from 'class-transformer';
 
 export class RequestOtpDto {
   @IsNotEmpty()
@@ -10,6 +11,7 @@ export class RequestOtpDto {
 
   @IsNotEmpty()
   @IsString()
+  @Transform(({ value }) => value?.toLowerCase())
   @ApiProperty({ example: 'zhivan', description: 'restaurant slug' })
   slug: string;
 }
diff --git a/src/modules/auth/dto/verify-otp.dto.ts b/src/modules/auth/dto/verify-otp.dto.ts
index ec1c6f1..9836479 100644
--- a/src/modules/auth/dto/verify-otp.dto.ts
+++ b/src/modules/auth/dto/verify-otp.dto.ts
@@ -1,5 +1,6 @@
 import { IsNotEmpty, IsString, Length, IsMobilePhone } from 'class-validator';
 import { ApiProperty } from '@nestjs/swagger';
+import { Transform } from 'class-transformer';
 
 export class VerifyOtpDto {
   @IsNotEmpty()
@@ -16,6 +17,7 @@ export class VerifyOtpDto {
 
   @IsNotEmpty()
   @IsString()
+  @Transform(({ value }) => value?.toLowerCase())
   @ApiProperty({ example: 'zhivan', description: 'restaurant slug' })
   slug: string;
 }
diff --git a/src/modules/auth/services/auth.service.ts b/src/modules/auth/services/auth.service.ts
index b6844eb..fb18bfa 100644
--- a/src/modules/auth/services/auth.service.ts
+++ b/src/modules/auth/services/auth.service.ts
@@ -40,6 +40,13 @@ export class AuthService {
   async requestOtp(dto: RequestOtpDto, isAdmin: boolean) {
     const { phone, slug } = dto;
     const normalizedPhone = normalizePhone(phone);
+    
+    if (isAdmin) {
+      const admin = await this.adminRepository.findByPhoneAndRestaurantSlug(normalizedPhone, slug);
+      if (!admin) {
+        throw new BadRequestException(AuthMessage.ADMIN_NOT_FOUND);
+      }
+    }
     const code = this.generateOtpCode();
     const key = isAdmin ? this.adminOtpKey(slug, normalizedPhone) : this.userOtpKey(slug, normalizedPhone);
     await this.cacheService.set(key, code, this.OTP_EXPIRATION_TIME);