Go to your Purchase History are there any unknown purchases there? Does anyone in your household have access to your account, perhaps made Guest Purchases? These would not show on your account.
Best to contact eBay Customer Services ask if they sent these codes, and why.
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.
@khokon
