That is the standard label sent.
For that heavier weight label required contact eBay Customer Services, their lines are open now. They'll reissue the correct label, and charge it to the seller's account.
To Contact Customer Services, I find the quickest way to contact them, either for a Live Chat, or you can select to speak and request a Call Back, to click on this link:
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
On weekdays lines open between 8 a.m. and 10 p.m.
On weekends they open between 9 a.m. and 6 p.m.
