I had a $400 Costco Cash card that I sold on the internet for $350. The buyer from another state paid me by check and told me to ship regular USPS mail with tracking number.
A few days later, buyer emailed me saying that he did not receive the card and asked his money back. I tracked the status on www.usps.com and it said package delivered.
Buyer threatened to report me to the police and charge me. What would I need to do?