What has been the problem with the phones? Quality of the call? Phone breaking? Or is he honestly tossing them off of a tower?
I don't know about AT&T but I know with Verizon if the phone isn't getting good reception you can take it back (within 30 days I think).
My husband used to buy a G'Zone (by Casio) because they are rugged - drop proof, water proof, shock proof, basically ... husband proof. He LOVED his first one, then he got the new-improved model and the call quality was POOR. He took it back to Verizon and we both got I-Phones. The I-Phone isn't indestructable like his G'Zone phone was, but the call quality is fantastic. As a bonus we are both discovering all other wonderful things we can do with an I-phone - like get instant weather updates (pretty handy when you work in the field), check e-mail, send pictures ("Is this the right part boss?"), maps, I have a compass on mine and a stud finder too. They really are amazing little devices.
If he's tossing ... I mean *dropping* them off a tower then look into getting the insurance with your carrier and they will replace the phone when it is dropped ... I mean *falls* from 100 + feet.
With the pay-as-you-go phones ... (at least the service I have that we use when we are in England) you have to purchase the telephone outright. If you purchase a cheap phone, you get a cheap phone with lousy reception. If you purchase an expensive phone with good reception and it falls off of a tower ... your still out the $$ for the phone. You're not "renting" the phone, your only renting the phone service for a limited amount of time.