PALM DESERT, Calif. -

Can't wait for the end of your contract to upgrade your phone? Many companies offer trade-in programs and now, so will the world's biggest retailer.

Walmart announced Tuesday it will launch its new Smartphone trade-in program Sept. 21, joining Target, Best Buy and GameStop who already do it. It's no coincidence Walmart announced the news hours before Apple unveiled its latest iPhones.

"When people are going to be thinking about potentially upgrading, we wanted them to know that they can turn in their phone and apply it to purchase the new one," said Sarah McKinney, a Walmart spokesperson.

Here's how it works, take your phone to Walmart or Sam's Club and answer several questions about the quality of your phone. Based on your answers and the type of phone you're trading in, the retailer said people will likely get a credit for anywhere between $50 and $300 to spend on their next phone, "Anything from the iPhone 5, 4, 4S, or Samsung Galaxy S4," said McKinney.

"If it's more affordable I think it's a great idea. Help out the public," said Flori Trinidad, of Desert Hot Springs.

Some companies that offer trade-ins give a gift certificate for the entire store and some even give cash. Walmart will only allow customers to use the money to buy another phone. Trade-ins cannot be done online.