If you bought over the counter postage at your Post Office, you should be able to manually change/ edit that tracking number where you marked the item as dispatched if not, contact eBay Customer Services, they will do this for you, their link below.
As long as you didn't select Simple Delivery and bought your postage from eBay, then you can void that label and receive a full refund.
Find your label with this link . https://www.ebay.co.uk/ship/lmng/labels-history/seller-hub and to the left of the sales record there is a drop down menu under 'Actions' click on that , then click on 'Void Label'.
The refund will take between 5 - 21 days to process.
If you need to, 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.
@keferichards
