How do I change cell phones?

I am not changing cell phone providers, I just want to switch my cell phone from the one I have to a blackberry that I am buying off ebay. Also, I have AT%26amp;T, and I was wondering if I can buy a Verizon phone and use it with my service. Do I just switch SIM Cards?



Thanks!How do I change cell phones?
You can't use a Verizon phone with AT%26amp;T. Verizon is CDMA which is incompatible with AT%26amp;T's GSM network. Verizon phones are locked to Verizon and cannot be unlocked even to use on another CDMA network.



If you buy an AT%26amp;T blackberry, all you have to do is put your sim card in. Any other GSM blackberry will have to be unlocked before you can use it.