You've been a member for almost 20 years - how can you not know what the process is when someone does not pay?
If buyers do not pay after 4 days, it generally means that they have changed their mind and are just messing you about. Sending messages is useless if you have a non-responsive buyer. You have up to 30 days to cancel a sale. Not sure what happens after that as I would never let it get to that stage, but it might be worth your while to get in touch with Ebay Chat during business hours as I assume you have left it longer than that?
Of course Ebay will charge you a percentage - for all they know, the buyer could have collected it from your house and they are entitled to their fee. They are not responsible if you have left it too late!
Cancelling a transaction with the reason "buyer did not pay", is a strike against the buyer. Many here on the forums have their buyer blocks in place for those people who make it a habit of not paying.
