Trade ins?

The rep in a corporate store claims that they will give me $1000.00 for my old Galaxy SIII that’s been sitting in my drawer forever without a battery. I told him that I would buy a battery and see if it still powers up, and he said don’t waste my money, they won’t check a phone that old. He claimed that because it’s branded Verizon on the cover he’d accept it. I’m finding it hard to believe that a Verizon representative working in a corporate store has the final word on trade in devices. Is he going to accept it and someone else farther up the line going to veto his decision, leaving me with a balance due? I did ask him point blank almost word for word the same question and he said as long as I bring it in personally I wouldn’t have any problems. Sounds way to good be true to me, but he was pretty convincing. Someone please help a old man out, Verizon is the only cellular game in town where I live so switching carriers isn’t an option until AT&T or T-Mobile figure out that us old rural hillbillies have figured out how to use cell phones and some of us even have email now.