diff --git a/src/Service/CustomerHandler/CMBCustomerHandler.php b/src/Service/CustomerHandler/CMBCustomerHandler.php
index d8107514..f66a8e30 100644
--- a/src/Service/CustomerHandler/CMBCustomerHandler.php
+++ b/src/Service/CustomerHandler/CMBCustomerHandler.php
@@ -320,7 +320,9 @@ class CMBCustomerHandler implements CustomerHandlerInterface
         $nerror_array = [];
         $verror_array = [];
 
-        // TODO: validate mobile numbers
+        if (!($this->validateMobileNumber($req->request->get('phone_mobile'))))
+            $error_array['phone_mobile'] = 'Invalid mobile phone number.';
+
         // TODO: validate vehicles
 
         // custom validation for vehicles
@@ -685,6 +687,18 @@ class CMBCustomerHandler implements CustomerHandlerInterface
         }
     }
 
+    protected function validateMobileNumber($mobile_number)
+    {
+        if (empty($mobile_number))
+            return true;
+        if (strlen($mobile_number) != 9)
+            return false; 
+        if(preg_match('/^\d+$/',$mobile_number))
+            return true;
+
+        return false;
+    }
+
     // check if datatable filter is present and append to query
     protected function setQueryFilters($datatable, &$query) {
         if (isset($datatable['query']['data-rows-search']) && !empty($datatable['query']['data-rows-search'])) {