You'll either have to wait until the 25th of Sept. until AT&T decides they want to release it or you can use third party apps like Get MMs or Swirly which are kinda complex to… use and I would not recommend because you have to Jailbreak or hack your phone with Cydia which has been known to mess up certain i Phones like the G2. There is an app out there from ifind2 called send MMS which doesn't require you to do all that and it works with i phone and all other cell phone providers; just check it out the home page is http://MMS.ifind2.com (MORE)
\nThere is a small chance you have no enabled 3G. To do this follow these steps.\n.
\nGo to Settings > General > Network and Enable 3G should be set to on.\n.
\nAlso you…r area may not have 3G capabilities. In this case there is no 3G signal for 3G to work. To check 3G coverage contact your provider.\n.
\nAlso if your iPhone is a 1st Generation and not the iPhone 3G you do not have 3G capabilities. (MORE)
the sim card just holds network information not phone information so yes you can transfer your sim card without any problems i had a sim card from about 3 years ago and i just… bought a iphone 3gs and it works fine in it (MORE)