I know AT&T does this for a monthly additional fee, but I have no idea if Verizon does it. If they did with a different model phone, then I am sure they can do it with the iPhone on their network.
I've never heard of it called a ringback. Me being a a PC techie, the last time I heard ringback was when you were calling for company network access, and after you called the number and entered a code, the system would call you back. It was good for avoiding long distance charges. This was of course, back in the day before Wifi and OTA data connectivity.