Do you have an android phone? If you do, and you have the fi app installed, if you turn off the cellular network, and connect to wifi only, you get unlimited calls and texts to the US on any plan over wifi. Wifi calls and texts don't work with Apple phones unfortunately.
I've used fi for about 5 years. No problem using the wifi calls and texts nearly daily while overseas. If you use too much data overseas, they will stop your data. That happened to me a couple of times, but got reset after I returned to the US for a few weeks. Calls and text still worked even though they stopped the data.