In Brazil wireless credit card terminals are also very common, and all I've seen use cell phone radios, so they work anywhere a cell phone from the same telco would work. Once in a while you still see the old wired terminals (which use wired phone lines), they are slower since they have to dial to the backend. And of course there are the terminals wired directly to a POS terminal (but places with these usually have wireless credit card terminals as a backup).