Can't thank you enough for posting this info. I have been on the phone with T-Mobile support for two day and numerous techs to no avail. They left me without connectivity saying they would check into it and call within 48 hours.
I have googled this issue on my phone before but never found this thread. Today it came up at the top of the list. I followed your steps and am up and working again.
Too bad T-Mobile techs don't read their own forum.
Thank You!!!