I sold a rocking horse on craigslist Dec. 18 for $50. The horse makes horsey sounds while the child is rocking. I put in fresh batteries and before I listed it and the horse was making sounds as normal. The people bought this for their 2yo for Christmas. The day the husband picked it up, I got an email from the wife saying the horse is great. Now 11 days later, they call and say the sound isn't working and want their money back. This horse was in like new condition when they bought it. What should I do?