eBay do their best to hide their phone number. You're meant to be able to get hold of it, and the PIN to go with it, by following my link above but, like many websites, it's easy to find yourself going around in circles!
Try signing into your eBay account first and then going here:
https://www.ebay.co.uk/help/buying/default/ask-ebay-to-step-in?id=4701
Then EITHER use the links to ask eBay to step in OR click 'Contact Us' at the foot of that page to access the automated help system. (If it can't work out how to answer your query, it will hand you over to a real person).