We are currently using T-Mobile and have for years.  When we went overseas we could purchase a plan while we were overseas which gave us free calls within Europe and to the US along with free texts and 20 gb of data up to 4g or 5 g speed.  This worked great but at the end of our trip we got a nasty note saying that this wasn’t intended for extended use and now and we can no longer use it.  We are leaving for France in March and will be in Spain for a short period and in France for about 10 weeks and then in Great Britain for 3 months and then back in France for 90 days.  We will be mostly in small places.  We want data and calls.  We’d appreciate your suggestions.

It has been a bit since I looked, but I think Orange has a sim card and plan that covers most of Europe for calls and data. Another option is to have a voip plan like voip.ms which will give you calling options to most destinations when 8you have wifi or data, so during a hotel stay you'd not be using up your data.

I believe the Orange sim cards are available in airports and shops all over.

Did T-Mobile give a definition of "extended use"? IIRC, our plan has free text/data, but calls cost. I don't think it's even offered any more. We probably won't be gone for more than a month at a time, but it would be good to know if they might do the same to us.

You should be fine.  We’ve been overseas a minimum of 3 months and sometimes longer.

Susan Carpenter also mentioned the Orange SIM card.  We infrequently make calls where we are staying it’s mainly for calling places where we will be staying or for them to call us with occasional calls to each other.  We also need data so we can track each other on our gps’s and use for a hotspot for our iPads when where we are staying have poor WiFi.

I was shocked to discover that Sprint is one of the best overseas options. In 2019 I spent a few weeks in Korea, and 6 months in Germany with work trips to Poland and Lithuania.  Calls using Sprint from almost anywhere outside the U.S. are billed at 0.25 per minute.  So I could call home for a few minutes for 1 U.S. dollar.  Of course, if you have wifi available, then there are no-cost options.

You can also consider a prepaid sim card for Europe. You can keep your T-Mobile sim for when you're in the US but pop in a regional sim card while overseas.  https://www.simoptions.com/best-prepaid-sim-card-europe/

I’m not sure of keeping T-Mobile since I’d be paying for 9 months when I’m not using for anything but forwarding messages but I’m definitely thinking about a SIM card but also thinking about googleFI if it has good coverage in France and Spain in smaller villages.  I’m still researching though.

I have Viber and Skype accounts for when I actually make international phone calls while overseas but your phone use is quite different than ours. It sure gets complicated when you try to find the best way to communicate without horrible charges.

My only experience is negative.  My wife bought a new Verizon phone a couple years ago and. knowing we had an upcoming trip to Europe, specifically asked if she could use it in Europe provided that she put an appropriate SIM card in it.  She was assured that yes, that would work.

When we arrived and tried to do exactly that, it did NOT work.  Evidently the phone is locked to Verizon's network and they want some ridiculous amount of money to unlock it or do whatever other voodoo they do to let it connect to networks outside their own, and outside the U.S.

She spent the better part of an hour on the phone with them - from our hotel room in France - before giving up.

She was so angry that when we returned she canceled her Verizon account and switched to T-Mobile.  We've not tried to use that phone outside the U.S. and I do not know the specifics of her plan so I have nothing to offer by way of information there.

I'm thinking a pre-paid phone purchased in Europe might be an option?