diff --git a/apps/users/api/serializers.py b/apps/users/api/serializers.py
index 9a97de8..0c678b0 100644
--- a/apps/users/api/serializers.py
+++ b/apps/users/api/serializers.py
@@ -6,6 +6,11 @@ from core.serializers.base import BaseModelSerializer
 
 User = get_user_model()
 
+INVALID_MOBILE_FORMAT_MESSAGE = "فرمت شماره موبایل نادرست است."
+INVALID_MOBILE_NUMBER_MESSAGE = "شماره موبایل معتبر نیست."
+PASSWORD_MISMATCH_MESSAGE = "رمز عبور مطابقت ندارد."
+NEW_PASSWORD_MISMATCH_MESSAGE = "رمز عبور جدید و تکرار آن مطابقت ندارند."
+
 
 class UserProfilePictureSerializer(BaseModelSerializer):
     class Meta:
@@ -39,10 +44,10 @@ class RegisterSerializer(serializers.Serializer):
         re_password = data.get("re_password", "")
 
         if not (mobile.isdigit() and len(mobile) == 11):
-            raise serializers.ValidationError({"mobile": "فرمت شماره موبایل نادرست است."})
+            raise serializers.ValidationError({"mobile": INVALID_MOBILE_FORMAT_MESSAGE})
 
         if password != re_password:
-            raise serializers.ValidationError({"password": "رمز عبور مطابقت ندارد."})
+            raise serializers.ValidationError({"password": PASSWORD_MISMATCH_MESSAGE})
 
         return data
 
@@ -54,7 +59,7 @@ class SendOTPSerializer(serializers.Serializer):
 
     def validate_mobile(self, value):
         if not value.isdigit() or len(value) != 11 or not value.startswith("09"):
-            raise serializers.ValidationError("شماره موبایل معتبر نیست.")
+            raise serializers.ValidationError(INVALID_MOBILE_NUMBER_MESSAGE)
         return value
 
 
@@ -65,7 +70,7 @@ class LoginOtpSerializer(serializers.Serializer):
 
     def validate_mobile(self, value):
         if not (value.isdigit() and len(value) == 11):
-            raise serializers.ValidationError("فرمت شماره موبایل نادرست است.")
+            raise serializers.ValidationError(INVALID_MOBILE_FORMAT_MESSAGE)
         return value
 
 
@@ -75,7 +80,7 @@ class LoginSerializer(serializers.Serializer):
 
     def validate_mobile(self, value):
         if not (value.isdigit() and len(value) == 11):
-            raise serializers.ValidationError("فرمت شماره موبایل نادرست است.")
+            raise serializers.ValidationError(INVALID_MOBILE_FORMAT_MESSAGE)
         return value
 
 
@@ -90,7 +95,7 @@ class GoogleOAuthCompleteSerializer(serializers.Serializer):
     def validate_mobile(self, value):
         normalized = "".join(ch for ch in value if ch.isdigit())
         if len(normalized) != 11 or not normalized.startswith("09"):
-            raise serializers.ValidationError("فرمت شماره موبایل نادرست است.")
+            raise serializers.ValidationError(INVALID_MOBILE_FORMAT_MESSAGE)
         return normalized
 
 
@@ -105,9 +110,14 @@ class ResetPasswordSerializer(serializers.Serializer):
     password = serializers.CharField(write_only=True)
     re_password = serializers.CharField(write_only=True)
 
+    def validate_mobile(self, value):
+        if not value.isdigit() or len(value) != 11 or not value.startswith("09"):
+            raise serializers.ValidationError(INVALID_MOBILE_NUMBER_MESSAGE)
+        return value
+
     def validate(self, data):
         if data.get("password") != data.get("re_password"):
-            raise serializers.ValidationError({"password": "رمز عبور مطابقت ندارد."})
+            raise serializers.ValidationError({"password": PASSWORD_MISMATCH_MESSAGE})
         return data
 
 
@@ -118,7 +128,8 @@ class ChangePasswordSerializer(serializers.Serializer):
 
     def validate(self, data):
         if data.get("new_password") != data.get("re_password"):
-            raise serializers.ValidationError({"new_password": "رمز عبور جدید و تکرار آن مطابقت ندارند."})
+            raise serializers.ValidationError({"new_password": NEW_PASSWORD_MISMATCH_MESSAGE})
+
         return data
 
 
diff --git a/apps/users/tests/test_api_views.py b/apps/users/tests/test_api_views.py
index caa558a..a34df04 100644
--- a/apps/users/tests/test_api_views.py
+++ b/apps/users/tests/test_api_views.py
@@ -65,6 +65,20 @@ class UserApiViewTests(APITestCase):
             mode="login",
         )
 
+    @patch("apps.users.api.views.generate_and_send_otp")
+    def test_send_otp_view_supports_forget_password_mode(self, generate_and_send_otp):
+        response = self.client.post(
+            "/api/users/otp/send/",
+            {"mobile": "09123330001", "mode": "forget_password"},
+            format="json",
+        )
+
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+        generate_and_send_otp.assert_called_once_with(
+            mobile="09123330001",
+            mode="forget_password",
+        )
+
     @patch("apps.users.api.views.login_with_password")
     def test_login_view_returns_tokens(self, login_with_password):
         login_with_password.return_value = {"access": "a", "refresh": "r"}
@@ -112,6 +126,21 @@ class UserApiViewTests(APITestCase):
             password="new-secret123",
         )
 
+    def test_reset_password_view_rejects_invalid_mobile_format(self):
+        response = self.client.post(
+            "/api/users/password/reset/",
+            {
+                "mobile": "9123330001",
+                "code": "123456",
+                "password": "new-secret123",
+                "re_password": "new-secret123",
+            },
+            format="json",
+        )
+
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+        self.assertIn("error", response.data)
+
     @patch("apps.users.api.views.change_password")
     def test_change_password_view_requires_auth_and_calls_service(self, change_password):
         self.client.force_authenticate(user=self.user)