Originally Posted by
msb0b
Sounds like you may have an VOIP app that registered itself as the international call handler. It is routing international calls over the data connection to save you money, but the data connection is not fast enough to support VOIP.
Google Voice, Hangout, Skype, WhatsApp, Line, just to name a few, can be set as the international call handler, sometimes without your knowledge. Dig through your VOIP or chat apps' settings.
Nope, none of those apps or, any others, on my phone. I'm not sure why so many posters are not comprehending that my carrier is AT&T and I'm ONLY using their Passport plan, to make/receive calls, send/receive texts and use cellular data while I'm overseas. It's $10/24 hour period (not day) for unlimited texts, unlimited phone calls and cellular data up to the limits of your plan. It works just as if I was back in the U.S. At the risk of repeating myself, it works like a charm.
If anyone wants more info, you may want to check AT&T's Passport plan page or similar page for other carriers. It really is quite simple and not as complicated as others are making it.