You cannot use a US Cellular phone on AT&T's network...or visa-versa; and here's why:

US Cellular uses CDMA technology. This means their cell phones do not even use SIM Cards...therefore, there is NO possible way for it to work. Along with US Cellular, there are many carriers who don't use SIM Cards. This is the list: Verizon Wireless, Sprint PCS, CriKet, Metro PCS, and various other regional carriers.

AT&T uses a technology called GSM. GSM uses SIM Cards. The two types of networks, CDMA or GSM, are incompatible. Along with AT&T another carrier that uses SIM Cards includes T-Mobile. Nextel uses iDEN which is said to be incompatible with both GSM and CDMA also uses a SIM Card.

Hope this helps.

I've got a phone I used with US Cellular and would like to know if there is any way I can use it with AT&T. I've been told you can't just switch the sim card. Is this true?
Any help would be appreciated.
Thanks
Daggie