Wal-Mart has announced a smartphone trade-in program wherein customers can bring in their old working smartphone and take home a brand new one, starting September 21.

Wal-Mart, the world's biggest retailer, may be following in the footsteps of Best Buy and Apple, but has announced its own smartphone trade-in program at the right time. Just hours before Apple is expected to unveil its new range of iPhone 5S and cheaper 5C devices, Wal-Mart's trade-in program will give customers a chance to upgrade from an older iPhone or any other smartphone to a brand new one. Not necessarily the new iPhone, but consumers can pick any model from a selection of more than 100 devices.

The retailer announced Tuesday that the new trade-in program will kick off September 21, 2013. Based on the condition and the brand, the older smartphone will fetch an instant credit of anything between $50 and $300, which can be redeemed to purchase a new smartphone. For instance, the trade-in value for a working, non-damaged iPhone 5 can get up to $300 credit, while Samsung Galaxy SIII and Galaxy S2 smartphones can get $175 and $52, respectively.

Customers can avail the credit towards the purchase of a new smartphone with a two-year agreement from AT&T, Verizon Wireless or Sprint or through Wal-Mart's prepaid contract-free Straight Talk Plan.

"Smartphones have become a part of our customers' everyday lives and as new devices launch more frequently, trade-in programs are becoming more popular," Steve Bratspies, executive vice president of general merchandise for Walmart U.S., said in a statement. "More and more, customers are choosing where they purchase new smartphones based on where they'll get the best value for their trade-ins. Our goal is to give them more value for their old devices and the lowest price for their new one - all part of our promise to be the best destination for wireless."

Customers can walk in to the electronics department of any of the more than 3,600 Wal-Mart Stores and Sam's Club outlets across the country.

So if you are eager to upgrade your older smartphone for a different brand like the new iPhone 5S or the 5C, then here is your chance. In the coming months several other smartphones are also likely to hit the market and buyers will have a wide range to choose from.