ATT uses GSM while sprint uses CDMA and iDEN. This basically means that the cellular radio is a different technology. The same phone is actually a different model (for example ATT might have the touch 2 phone model 1000x while Sprint has the touch 2 phone model 1000y and US Cellular has the touch 2 phone model 1000z) for different companies because the hardware (radio) has to be different. Right now I believe that one can interchange ATT and T-Mobile phones with one another and Verizon and Sprint can be interchanged. I do think that all networks will be a shared technology when the 4G networks start rolling out next year, but don't quote me on that. That said, it will take quite a while to get full-on 4G coverage especially in Iowa

There are a few things that I miss about living in Cali LOL.