Tomorrow on 23rd At&t will give credit towards a phone with a trade in.

Boy Genius report

We have just been told that beginning January 23rd, AT&T will be starting a handset trade-in program. This is the same day AT&T’s new SMS plans are set to take effect. AT&T devices as well as phones from other carriers will be eligible for the trade-in offer. Outside of applying the resulting credit toward a new purchase at AT&T, the carrier will also give you the option of taking a check or donating the money to charity, which AT&T will do for you on your behalf. And you thought Christmas was only in the month of December? Hit the break for a full shot of an internal AT&T document that details the new program.
on quote from comments
kinda sounds familiar...oh yeah that's right, VZW already has something like this. Does at&t just copy everything vzw does? In any case, it's better just to sell your phone on ebay since you will get way more money from either vzw or at&t for your phone.
Yes yes both Verizon and At&t are carriers,they are not in the used Cell business.