I have had T-mobile for the past five years or so and have the plan that allows for use in around 200 countries. I've always had excellent service in numerous trips to Cozumel and during a trip to Costa Rica. In 2019, I spent eight weeks traveling in Europe and my phone worked everywhere we went; Norway, UK, Denmark, Italy, Germany, France, Switzerland...I think you get the idea. Towards the end of our travels, i did get a warning message from T-Mobile that I was using my "overseas" cell service too much and that they might have to slow things down, or I might have to sign up for a different plan if I was going to continue to use it overseas. Best way to avoid that is to be on wifi as much as possible. I live in Colorado and T-Mobile works better outside the United States that at home. I just replaced my very old iPhone 7 with the iPhone 12 with 5G and my service here in Colorado seems to be much better.