Got old phones wasting away in a junk drawer? Trade 'em in for cash.

Every year since 2010, smartphone sales have exponentially increased year after year, to the point where we can expect 2016 to surpass 1.5 billion units sold. With all those new phones getting into customers hands, there must be a similarly huge number of unwanted, old phones.

To combat all that technology waste, Sprint — along with all the other major carriers — have buyback programs for your old phones to be refurbished and resold, or recycled properly. But what sets Sprint apart from other carriers' buyback programs, such as Verizon, is the ability to trade in up to five old phones per active line in a calendar year.

Whether you're an existing Sprint customer, or considering switching over, you can easily find out the trade-in value of your old phone and then decide whether to head into a Sprint store and trade it in towards a new phone or accessory, ship it (for free) to Sprint for the applicable account credit, or, if your old phone doesn't qualify for credit, choose to have Sprint recycle your old phone, with the net proceeds donated to charities via Sprint Project Connect.

How does it work?

The first step is finding out how much your phone is worth. Sprint has a list of accepted devices with the buyback credit available for each, or you can start the process by entering your phone's information online, which instantly determines the credit value of your device. Then it's simply a matter of either heading over to a Sprint store in person, or printing your free shipping label and sending your device or devices to Sprint for processing. Once you've sent your devices in, you'll be given a confirmation number which you may use along with your account number and the phone number associated with your account to check on the status of your trade in while it is being processed.

What if they determine my phone has no value?

Sprint has a recycling program that partners with charities via Sprint Project Connect to fund internet safety resources for kids. On top of helping to support a good cause, the reality is phones and other electronics should never end up in landfills. So do your part and properly recycle your old, derelict devices and help keep kids safe on the internet at the same time. It's win-win.

What should I do with my device before trading it in?

It's very important to note that you alone are responsible for removing all confidential, proprietary and personal information from your phone and any associated memory cards. A factory reset should do the trick, but Sprint also provides eight tips to wipe your phone of all personal inforrmation.

How quickly will I receive my trade-in value?

If you go into the store, you're able to use the available credit instantly towards the purchase of a new phone or accessory.

If you go through the online process and ship your phone in, Sprint says it can take up to three billing cycles for the credit to appear on your account. If three billing cycles pass by with no sign of the credit, you'll want to contact a representative from Sprint's buyback program.