We have no access to your account so cannot see any charges, that is, if postage unused was not refunded, or perhaps a duplicate purchased .
This will show you a breakdown of your transactions, fees / postage promotion fees paid.
https://www.ebay.co.uk/sh/fin/transactions
If this doesn't explain the charges contact eBay Customer Services who have access to your account and can explain any transaction fee for you.
Contact them tomorrow as only ' automated agents' are available now.
This is the easiest and quickest way to contact eBay Customer Services, for a Call Back option.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
Lines open 8 a.m. - 10 p.m. on weekdays
9 a.m. - 6 p.m. on weekends.
Automated agents will be available on chat outside of the above hours.
I recommend contacting CS first thing in the morning as there's more chance of Dublin answering.
@goodfinds1st