Exchange denied

I went to exchange some gifts that either didn't fit and a couple of my kids toys that did not work. They said it was declined due to bad checks on record. I called telecheck and they say that their is nothing on my record. Gave me a number to another company that said they would contact me in 7 to 10 days. I thought Wal-Mart had a guaranteed refund policy. This whole thing sounds like a scam to make money.