Implementing multi-party calls with VoIP and GSM using the Programmable Voice API allows for seamless communication between multiple users, including translators and aid workers. This guide focuses on building a robust infrastructure to handle dialing in other users, using only their phone numbers, behind the scenes. The backend is built using Python Flask App for Twilio, and endpoints are called from the frontend (Web/Mobile App) and the Twilio console. To complete this tutorial, one needs a free Twilio Account, basic working Python Flask App for Twilio, a Twilio Phone Number, a Programmable Voice TwiML App, an Amazon S3 Bucket, and a Frontend App that communicates with the Twilio Console / Flask App. The guide outlines how to set up conferences as agent conferences, create a voice request URL for the TwiML App, start a call, add the caller to the conference, handle edge cases such as when only one person is left in the conference or the original caller leaves before the callee picks up, and end the conference call.