You can buy a handset through an electronics retailer. But:
- Every cell carrier in the US has its own frequencies, so you generally have to buy a handset specific to a particular carrier. (The GSM carriers, T-mobile and AT&T, share the voice and 2G data frequencies, but they have different 3G data frequencies. The CDMA carriers share nothing.)
- With most carriers, when you start service you are paying a baked-in surcharge designed to pay for the discount on the handset you got from them. You pay this whether you bought the handset, or brought your own. So if you buy a handset and then set up a plan, you're throwing money away if you don't buy it from the carrier. (There are some carriers for which this isn't true.)
- Every cell carrier in the US has its own frequencies, so you generally have to buy a handset specific to a particular carrier. (The GSM carriers, T-mobile and AT&T, share the voice and 2G data frequencies, but they have different 3G data frequencies. The CDMA carriers share nothing.)
- With most carriers, when you start service you are paying a baked-in surcharge designed to pay for the discount on the handset you got from them. You pay this whether you bought the handset, or brought your own. So if you buy a handset and then set up a plan, you're throwing money away if you don't buy it from the carrier. (There are some carriers for which this isn't true.)