I currently nave a Bold2 from AT&T and would like to know if I moved to TMobile, will the phone have all the TMobile functionality including the ability to route phone calls over WiFi (UMA) and TMobile 3G.

The phone is unlocked.

Wirelessly posted

No and no. UMA requires hardware as well network features. And tmo uses different 3G frequency.

And before you ask, NO, there is no way to change the settings... sell it on eBay and buy a device designed to work with your provider. PERIOD.