I'm not talking about data. The major carriers use different radio technologies, Bean007. Why do you think there were different versions of the iPhone and others produced? I seriously doubt you can use a phone with a GSM radio on a CDMA network with much success, even if you could get the network owner to activate your phone on it.
This is just useless.
Fact of the matter is that when you buy a subsidized phone from a carrier or they give you the phone for free especially smart phones they lock you in for the contract.
That contract if completed with the requirements for the phone makes you pay the full unsubsidized price + more when the 2 years are completed. Now if you buy a CDMA phone you can only take it to another CDMA network (Sprint, Verizon, Virgin Mobile, Metro PCS, etc) and if you buy a GSM phone you can only take it to another GSM network (Att, Tmobile, etc)
So it is best to just buy your own unlocked GSM or CDMA phone and use it on the carrier you choose.
Home of the free, and perpetually enslaved.
I don't know how you people can put up with such BS from companies.
A bit different in Aus...
The vast majority of phones under contract can be easily unlocked at any time to work with any carrier. Handy when travelling overseas.