T Mobile service with US plan in Germany

T Mobile's Simple Choice plan include unlimited data usage overseas but the catch is that the speed is throttled down to 2G. Which for anything but text is painfully slow. If you want 4G speed, you can buy a one-time two week/500GB pass for $50USD.

If you have a T-Mobile Simple Choice plan in the US, and you go to Germany:

1) Texts are free and unlimited.
2) Internet is free and unlimited at slower speeds. It used to be 2G, but I got 3G in Israel and am, as I write, getting it in Madrid; someone who worked in my T-Mobile store said she got 3G in Dubai and her coworker got it in Switzerland. Sometimes my phone has even said 4G LTE in Madrid; I made a panicked call to T-Mobile to make sure I wouldn't be charged for this, and they said I wouldn't be. But that brief appearance of faster speed appears to have been a fluke. As Michael said, if you want or need consistent faster speed, you'll pay extra (more than you would with a local SIM).
3) Calls are $0.20 per minute (to send or receive, to or from anywhere).

It's a great deal, particularly for those who want or need to keep their US number.

A few points to be careful of:

1) You must have a Simple Choice plan; other T-Mobile plans have different, much higher rates for foreign use.
2) If going beyond western Europe, you have to check the list of included countries carefully. For instance, some of former Yugoslavia is included, but some is not.
3) T-Mobile no longer has contracts, but they are trying to make it harder to start, stop, and then restart this service (they want people using it domestically too, not just for travel). I don't know the latest details, but don't assume you can "suspend" it when you're not traveling. Of course, if you can switch to them for your US needs, you're set.

Sometimes my phone has even said 4G LTE in Madrid

I have gotten the same screen message of getting a 4g or 3g signal, but my experience is that the speed is still being throttled down to 2G speeds regardless of what signal the phone is connected to:( AFAIK actual 2G signals don't exist anymore in order free up more radio spectrum.

I have called Tmobile and got conflicting information, but the bottom
line is - it sounds like if you have Tmobile and are in Germany, your
datat cost will just as they are in the US (no international fees) as
long as you are hitting on Tmobile towers, but if you hit other
towers, you could get roaming fees.

No matter which service provider your T-Mobile USA phone connects to you won't have roaming charges. The only way you get extra charges is if you respond to the text message asking if you want faster data.

While T-Mobile USA phone might connect to T-Mobile in Germany, it also may not, so don't be alarmed as there is nothing to worry about. I can understand why your customer service rep. might give different answers. Many of them aren't world travelers and this stuff is complicated.

"Calls are $0.20 per minute (to send or receive, to or from anywhere"

If you are on wifi you can do "wifi calling" and calls are free.

We did this while in the Caribbean and it worked fine.

Just got back from Germany using our T-Mobile phones. No data or text charges. T-mobile will guarantee 3G which we seemed to get with very good consistency. As T-Mobile is a German company, you should expect great coverage, and we went there expecting 4g or LTE but this is a service you must pay additional for (which is why T-Mobile USA will only guarantee that speed). We got by just fine on our 3G and the wifi we had in places like our hotels.

Phone is .20 per minute to call back home, but I have not confirmed what the cost is to call locally while there.

If you are looking to make a lot of calls while there, getting a local sim will usually be a better value.

I just returned from Germany, Switzerland and Austria on a RS tour. I had Sprint, my tour guide had T-Mobile. I figured he has better knowledge of these thing than me. I wasn't happy with Sprint, so I switched to T-Mobile when I returned home and the salesperson told me that if I purchased a T-Mobile phone, rates would be $.20 a minute to the US and zero if I am on Wi-Fi. Deutsche Telecom owns T-Mobile and I assume a lot of the phone connections throughout Europe are simpatico with Deutsche. You may want to beef up your capacity for data if you use a lot, just so you won't get slowed down and then go back to what you might normally need when you return home. Ray G

Thank you, all, for the great feed back. This really helps!