Hi aperfo.. eBay will automatically bill the payment method set up when you opened the seller account. Seller account invoice should indicate that.
Can make a one time payment but do not do if ebay is processing an automatic payment..
http://pages.ebay.ca/help/sell/one-time-payment.html
I see one sold on the 24th of Dec. Are you saying the buyer didn't pay?
For non paid no communication..An unpaid item dispute should be open to recover the final value fee charged by ebay. Must do within 32 days. Close after 4 days and ebay credits..
http://pages.ebay.ca/help/sell/unpaid-items.html
Occasionally both buyer and seller mutually agree to cancel a transaction. Here is how to handle..
http://pages.ebay.ca/help/sell/cancel-transaction-process.html
Need to know that buyer agrees and will accept when eBay asks.