Just to add: the 3g/4g thing is carrier-dependent, as some carriers in North America have used the term '4g' as a way of marketing improved/enhanced 3g technologies.
Thanks everybody for the help...Craig, I think what you're saying is what I found out. What I was told was, although Tmobile says they're a 4g carrier, doesn't mean you'll have 4g in your city as it's mostly in the large metros like NY, Atlanta, LA., etc. Memphis is large but not large enough for them to have it here. Mostly as was said, it's a marketing ploy, yes they can legally say they have it but they're just not tell you the whole truth.

I pulled the trigger last night and changed over to Cellular South. My lady and I both got the Galaxy S (3g, with the contract & instant rebates for 99.00 ea.), free activation, unlimited talk/text/data for 59.99 per phone with first month free, 2 car chargers, a skin for her phone and an otter box shell for mine. Out the door, tax & all for 335.00, alot of money, but for what we got...well, I'm satisfied.