So I bought an At&t iPhone 6 off of eBay with the intention of unlocking it and using it on verizon with my sim. So I went to unlock but they say I can't because the guy I bought it from hasn't finished paying his at&t Next payments on the phone. Ouch. So now I don't know what to do. I have contacted the guy on eBay but he hasn't responded. What to do...