Mine rang once also - however, I read about a scam where people hit call back and it goes to an offshore account that then bills you hundreds of dollars for "services". Basic rule, if was important, the would leave a message.
Told me I was entitled to a $100 gift card from Walmart and an American Express voucher since I visited their website. They did not say what that website was and the connection was terrible so if they identified the company I could not understand it. All I had to do was send them $4.95 for shipping and handling. I declined.