How to disconnect my iPhone 4 with out going into or calling Verizon?

About a month ago I bought an iPhone 4 on Craigslist and the guy said he was going to disconnect it the next day. It's still not disconnected. I already went into Verizon to see if they can contact him some other way, they said no haha big help. So how do I disconnect it without going into or calling Verizon or messing up the esn?

Jailbraking it should take off any locks assigned to the phone.

If you mean disconnect it as in his name is still on the phone and he should be paying for it, then all you have to do is call verizon's technical support and let them know what is going on. They will help you out a lot better than the Verizon store can.