Fatal error: Uncaught Error: Interface 'Vonage\Entity\JsonSerializableInterface' not found in /home/digitalproduct/public_html/onlinejobportal/vendor/vonage/client-core/src/Call/Dtmf.php:35 Stack trace: #0 {main} thrown in /home/digitalproduct/public_html/onlinejobportal/vendor/vonage/client-core/src/Call/Dtmf.php on line 35