AT&T recently announced a trade-in program designed to help convince existing customers to upgrade to a new smartphone. Starting today, AT&T customers can trade in their current handset for a credit of at least $100 to use towards the purchase of any smartphone the company sells.

Under the new plan, customers can trade in a device that is three years old or newer and in good, working condition. Customers could earn more than $100 - that's just the least someone would receive. The credit can be used on virtually any handset despite the fact that AT&T specifically showcases the Galaxy S4, BlackBerry Z10 and the HTC One 32GB. Interestingly enough, Apple's iPhone is absent from that list of high-profile devices although it appears to be included in the promotion.

The promotion isn't limited to just smartphones, either. If you have a qualifying feature phone or even a tablet, AT&T will take that too. Considering that most feature phones are probably worth far less than $100, the deal looks to be pretty sweet if you have an unused device of this nature.

In the event that you have a qualifying device to trade in but don't want a new smartphone, AT&T has you covered. They'll accept your trade in and you can use the credit to put towards your bill or even towards accessories for your current phone.

What do you typically do with old handsets? Do they find a second home with a friend or family member, do you hock them on eBay or simply store them in the closet - never to be used again?