There is a place on the website, perhaps a PDF of your last bill or something, that shows you the remaining balance. I had to dig around to find it, but once I did, I put an ad for my phone on Craigslist and had the phone sold within an hour. As I mentioned, it appears that they can't take payment for the phone if you originally selected to trade the phone in. You will have to wait the 14 days for them to bill you. That's where the confusion is coming from and what the in-store reps don't understand. They also don't know how to direct users to find vouchers for those who do want to mail their phone in. It would be much more simple is all corporate stores could accept trade-ins or if reps could easily find and accept payment for the remaining balance.