Yes, you do.(Not familiar with Ebay, though. Do you get access to the phone number of the person you are dealing with?)
You have to submit a contact information request. It's an automated thing. You enter in the eBay user's ID and the number of the item in question and you receive their contact details (including phone number) by email, but they also receive yours.
More info: -
http://pages.ebay.co.uk/help/search/members.html#2
If I consider an item too expensive to send via regular first class mail, I send it via courier, so I just ask the eBayer that's bought from me for a phone number as one is needed by the courier.