Documentation / tooling would probably be Twilio. Provider based on price depends on how heavily you use US vs World, and if it's SMS (and/or MMS needed) or Vo

Documentation / tooling would probably be Twilio. Provider based on price depends on how heavily you use US vs World, and if it's SMS (and/or MMS needed) or Voice or both and what volume you are operating at. For pure SMS with a balanced mix of domestic and international, I would probably suggest AWS Pinpoint at this point. Their international rates compared to Twilio are fantastic for all the locations I spot checked.