Apparently I need to go get the data on my old SIM card transferred to the new one. The manual says it will allow me to upgrade to Wi-Fi calling when it becomes available. I could probably pop the old SIM in there I guess. At least the wifi works fine.
Update: After trawling through the T-mobile forums, I discovered there was an update to Androild 2.3.6 available (the phone came with 2.3.5). After a few hours of futzing around and staying up far later than I should have, I got the update downloaded and installed. Then the phone told me that Wi-fi calling was available, but that my SIM card (I put the old one in to test) needed to be updated. Off to the store at some point.