Hello Sir, I am a seasoned filemaker developer (new to freelancer though), I had the privilege to work with large companies and corporations to solve their business problems. I worked on several projects requiring RESRT API communications with Filemaker Database. I read your project description and I am confident I could help achieve a reliable communication with your 3CX system. Some of the mentionable API integrations to Filemaker database that I have done were: Quickbooks, Google Calendar; Google Drive, Tableau. Looking forward to working for you to achieve your goal.