Grandstream IP PBX was proposed for basic calling features along with call recording, there arose a requirement of integrating the PBX with the client’s in-house CRM, based in overseas. The PABX was configured to integrate with their server locally deployed where an application was run by client CRM. The PABX was configured using a SIP trunk with client server deployed locally. The APIs were enabled and the server IP was whitelisted in the PABX in order to communicate securely with the server. The PABX port was changed to a random port which was then forwarded in order to access it remotely. The APIs for call fetching, recording a call were also tested and implemented. Similar integration process was repeated for their sister concern firm, EMPG Properties. Complication that arose during the integration was even after enabling the API the integration, process was not complete as the PABX was not allowing the Server IP to communicate with PABX. Several requests were logged with Grandstream support team and the troubleshooting steps advised were not serving the purpose, we tried to change the firmware of the PABX which helped in successful integration. There are 120+ extensions at Bayut office and upto 15 extensions at EMPG Properties.