iPhone was blacklisted by Verizon and got it removed from the blacklist

This situation mirrors mine almost identically, but T-Mobile has yet to tell me who put my phone on the blacklist, and why it somehow returned to working status upon returning to Denver from my trip to Pittsburgh. I still fear that when I travel again the same issue may arise. The other infuriating thing is that T-Mobile only offers to contact you by phone which is impossible if your phone isn’t working and you’re out of town with no access to another phone. That necessitates going to a T-Mobile store and having to beg them to contact customer service on your behalf after they insist on trying to restore the phone even though you tell them it’s been blacklisted.