Go through the correct channels to get your money back AND leave the negative feedback. If your rating is good, people see that it's an obvious retaliatory comment left in return. I've had the same trouble with 'littlemoscow'. I paid immediately, waited 3 weeks, sent two reminders, then after E bay got involved they decided to refund my money and tell me the item was no longer in stock. (A re-issue 7").
I gave them a neutral feedback and they returned one. They've had 33 negatives this year. I've had none. You can see straight away who's wrong. Be bold and shame them.
In case you missed the name of the E bay bad guys. It's littlemoscow