I haven't heard of T-M banning wifi hotspot usage. Supposedly, they "ban" tethering, but tests w. my BB in tethering works fine. (These were just tests - no long time heavy use.).
I think all TM Androids have the wifi hotspot feature. We used it a little bit on my wife's MyTouch 4G Slide last week rather than pay the $13/day the hotel wanted.
GoogleVoice (domestic call forwarding and cheap intl. calls) Use GV to give us a "home" number in a 2nd location
3 T-Mobile lines - Unlimited talk and text. 1G data on each line . $90/mo. We have had no landline in 8 years