sorry about your misfortune. that really sucks.
as for what you should do about it:
- my knowledge of ebay is limited, but i know they have some type of guarantee or protection from fraud. make sure you talk to someone at ebay asap.
- i've never heard of that method of payment (certapay) but i've never bought on ebay so maybe it's common and i just don't know. what i do know is that legit internet payment companies like paypal and the recently-launched google checkout have protections against fraud. talk to them right after you get off the phone with the ebay people.
- perhaps the bank you opened an account with can assist in getting your money back. i know certain credit cards offer this service, but i've never heard of a bank doing it. it wouldn't hurt to ask, though.
good luck and let us know what happens.