Fatal error: Uncaught Error: Class 'Nexmo\Client\Callback\Callback' not found in /var/www/microservices/vendor/nexmo/client-core/src/Message/Callback/Receipt.php:12 Stack trace: #0 {main} thrown in /var/www/microservices/vendor/nexmo/client-core/src/Message/Callback/Receipt.php on line 12