I followed instructions on site http://stackoverflow.com/questions/32078510/postman-twilio-rest-api#new-answer Couldn't get Postman to POST to Twilio . I always got error: { "code": 21603, "message": "A 'From' phone number is required.", "more_info": "https://www.twilio.com/docs/errors/21603", "status": 400 } I all had to do was change Body > form-data to Body > x-www-form-urlencoded Problem was Postman encodes + to %2B which breaks the POST Couldn't get Postman to POST to Plivo - a similar variation on from missing. All I had to do was changed Body from x-www-form-urlencoded to Body > Raw > JSON (application/json) {"src": "+17787380898","dst": "+16047202643", "text": "Hello"} Postman - https://chrome.google.com/webstore/detail/postman/fhbjgbiflinjbdggehcddcbncdddomop?h...