Every sale generates a charge for eBay’s Final Value fees, whether or not money changes hands. You needed to either cancel the transaction, or open an Unpaid Item Dispute. Both those actions get your fees automatically credited back to you.
If you didn't do this, then you will get a bill. You would need to contact eBay to explain that you are a new seller who didnt know the ropes, and request that credit. If the matter has gone to collections, it may be too late, but i don’t have any experience to draw from. Sorry.
