eBay does not have a public phone number for you to call at the moment.
Use the Help & Contact link at the bottom of the page and follow the prompts for your particular issue. You should see a "contact us" link near the bottom and that should eventually lead to a page with a chat or "Have us call you" option if you are in the US or Canada.
Otherwise you can ask a general question here or on the discussion boards, or try contacting eBay via social media:
https://twitter.com/askebay
https://www.facebook.com/eBay/
