unhappy individual

So this undesirable customer came in today and claimed the Sony PSP we sold him a week ago no longer worked. He wanted another one. He had his receipt from coming in last week and purchasing two Sony PSPs with a friend of his. But here's the kicker, the serial number on the PSP he is trying to return is worn off pretty well on the bottom and illegible. So I take the battery cover off and pluck out the battery. Underneath the battery is an information label which has the serial number printed. The receipt he has lists two serial numbers taken from the two PSPs he purchased last week. Neither of them matched. Plus, the item had some signs of wear and bumps from being dropped. I explained that there was nothing I could do because this simply was not one of the items he purchased from me. It must have come from somewhere else, now it is broken, and he is looking to unload it for a working one: SCAM. He gets irate, he has to be kicked out, he threatens to charge us with the police, yadayadayada. A different customer comes in and says he spotted the upset individual outside trying to wave down a paddy wagon in order to get a police officer to charge us. He is very well known to police. He is unsuccessful. Some light afternoon entertainment.