diff --git a/src/sms/dto/sms-account.dto.ts b/src/sms/dto/sms-account.dto.ts
index 33bdefa..3a4dcbb 100644
--- a/src/sms/dto/sms-account.dto.ts
+++ b/src/sms/dto/sms-account.dto.ts
@@ -20,7 +20,7 @@ export class UpdateSmsAccountDto {
   @IsBoolean()
   isBlocked?: boolean;
 
-  /** Null clears auto-block; omit leaves unchanged. UI sends tomans×10 as rials. */
+  /** Null clears auto-block; omit leaves unchanged. May be negative (credit limit). UI sends tomans×10 as rials. */
   @IsOptional()
   @Transform(({ value }) => {
     if (value === null || value === '' || value === undefined) return value === undefined ? undefined : null;
@@ -29,7 +29,6 @@ export class UpdateSmsAccountDto {
   })
   @ValidateIf((_, v) => v !== null && v !== undefined)
   @IsInt()
-  @Min(0)
   autoBlockBelowRials?: number | null;
 
   @IsOptional()