Bad ESN?

[csjoquist]

I recently bought a new blackberry on ebay. I know "buyer beware" but the seller was a store with an excellent rating and satisfaction guarantee so I thought I'd be safe.
When I tried calling Alltel to activate the phone they said they can't locate the ESN or that it is incorrect. I've also tried contacting the seller with no return.
Am I screwed here? Do I have to return the phone (if the seller ever calls back)? Is there some way I can find if the phone has a different ESN using its PIN?

[MobileMadness002]

Most carriers that program based on ESN (Electronic Serial Number) will only activate devices they have sold themselves and entered the numbers into their database. If they are not willing to add the ESN then yes, you are screwed.