Wow.. How STUPID can people get! I got aggravated from just reading that post! You must have the patience of a saint.. I'd just say "2 lessons does not make you an experienced rider, Sorry but this horse is not for you." and hung up.
Ugh! I feel for you. Good luck with the whole selling thing..
Maybe you should put on the ad "do not call me if you are NOT experienced. I don't have time for bull crap."