diff --git a/composer.json b/composer.json
index f1e6998..2bf31a8 100644
--- a/composer.json
+++ b/composer.json
@@ -9,6 +9,7 @@
     }
   ],
   "require": {
+    "ext-mbstring": "*",
     "php-smpp/php-smpp": "1.2",
     "illuminate/support": "^5|^6|^7"
   },
diff --git a/src/SmppService.php b/src/SmppService.php
index f0a3309..b44dfe7 100644
--- a/src/SmppService.php
+++ b/src/SmppService.php
@@ -224,7 +224,7 @@ protected function getSmppAddress($phone = null)
      */
     protected function sendSms(SmppAddress $sender, $recipient, $message)
     {
-        $message = iconv('UTF-8', 'UCS-2', $message);
+        $message = mb_convert_encoding($message, 'UCS-2', 'utf8');
 
         return $this->smpp->sendSMS($sender, $this->getRecipient($recipient), $message, null, SMPP::DATA_CODING_UCS2);
     }