I purchased 13 tickets on the way to the Improv. ...

I purchased 13 tickets on the way to the Improv. When getting there, only 12 tickets were emailed, so an additional ticket was purchased. I noticed they still charged me for 13 tickets on my cc statement. When I called and asked for a refund of the 13th ticket (they could see it was never used) - they said they dont give refunds. I now have to go through my credit card company to dispute the charge because THEY did not issue the ticket. HORRIBLE customer service.