Can anyone recommend an inexpensive flip phone that's compatible on the T-Mobile network?
It's only needed for basic voice service. So any dumb-phone should suffice. It can even be a used device.
Presumably it should be 4G comparable, in order to survive the 3G network shutdown.
Alcatel 4052W or 4051S (unlocked). You can find them on eBay.
Yes. I got a 4052 (Smartflip) and it works just fine for voice. It has internet too but I haven't bothered with that. My 4052 is locked to ATT but I've been using it on an ATT MVNO (FreeUp) without any problems at all.
The 4052W is locked to T Mobile and the 4051S is locked to Verizon. I have a 4051S but mine is unlocked.
Here's a picture of the 4052:
It's locked to ATT but I use it on FreeUp just fine. I didn't specify a letter after the number because I wasn't sure what the correct number was.
UPDATE: It's 4052R
What is the street price for these Alcatel flip phones?