I've never had T mobile and probably never will. I'll relate a story why;
Back when I was in telecommunications we had a system wide outage for all of our long distance traffic; data/voice the whole shebang. We had contacted with Tmobile to carry our network on some of their facilities and the problem was isolated to their network. We (our senior execs) were on the phone ALL night with the Tmobile execs as well as their technical people. I've never, and I mean never, encountered a group so incompetent, uncaring and unmotivated. A comment I made directly to their president. It stood out in my mind that their technical folks did not know how their network was routed, and when that was finally determined, did not know how to troubleshoot it. The problem was in the northeast if I recall.
Since that time I've had conversations with folks that use/used Tmobile and that perception has been reinforced. They may have improved but I've not talked to anyone that would make me think so. FYI/JMHO