Fatal error: Uncaught Error: Class 'Nexmo\Client\Callback\Callback' not found in /opt/lampp/htdocs/kuesioner/vendor/nexmo/client-core/src/Network/Number/Callback.php:33 Stack trace: #0 {main} thrown in /opt/lampp/htdocs/kuesioner/vendor/nexmo/client-core/src/Network/Number/Callback.php on line 33