Starting September 21st, Walmart and Sam’s Club will roll out a new program which credits customers up to $300 for their used smartphones. The credit will go towards the purchase of a new one. This deal will also include buybacks of iPhone 5 as well as Samsung Galaxy S3. Samsung users will only get up to $175 for their Galaxy smartphone. Customers will be able to choose a 2 year contract or opt for the prepaid straight talk service Walmart offers.