iphone question?

[E-Revonut]

Buying any smartphone, outright is expensive. I'm pretty sure you can use an unlocked phone on verizon but it still has to be a verizon model of the iphone. There are really two versions of the iphone, verizon uses one model and everyone else uses the other. The cellular systems are different among the different companies

[brijar]

Bit of phone info:
There are two types of cell phones in the US. GSM and CDMA. AT&T and T Mobile are the big GSM carriers. GSM phones use SIM cards to identify your account.
Sprint and Verizon are the big CDMA carriers in the US. CDMA phones do not have SIM cards. They are programmed to your account over the air. You would have to ask Sprint or Verizon to do that.
The iPhone 4s and the iPhone 5 have both a CDMA and GSM antenna in them, which is rather neat because you should be able to use an unlocked one on any carrier. I'm not exactly sure this is the case, though. I know the older iPhone 4 comes in a GSM version and a CDMA Verizon version.
I don't know which carrier you already have, but if you have Sprint or Verizon and are buying an iPhone 4s to work with them, be sure to check the ESN number of the phone to make sure it is not black listed. Phones that have been reported lost or stolen will likely have black listed ESN numbers and will not be able to be activated. The exception to this are services like Cricket wireless that do no share Sprint and Verizon's blacklist. But they don't have huge coverage areas nor very good tech support.

http://www.kittywireless.com/pageplus/validateesn.html
You can type in the ESN number and this tool will email you the results to see if the ESN is clean.

Good luck!