Verizon's the one with the REAL 30-day trial
Verizon is the carrier that offers the REAL 30-day trial, where they credit you back for pretty much everything if you don't like the service and return the phone. This is a matter of written policy, not "well if we like you and you kiss our *ss, you *might* get a credit on some of the fees" situation.
They are also the first major US carrier ever to pro-rate the early termination fee if you cancel before your contract term is up. They also have by far the highest customer loyalty statistics in the industry.
Do the research...