I was unable to get data for a month, until a rep at a different tmobile store fixed my "APN type". Previously, APN Type was set to "default", now it is set to "default,mms,supl". This was the only change he made, and it provided 4g (and 3g, etc) data service immediately. (See the 3 attachments for all my APN info.)
FYI, this fix was for a Droid Mini from verizon that I am using on t-mobile. Previously (before this OTA update from just before Halloween) I had the hand-off issue with making calls or sending texts, but this is now no longer a problem.