Buddy bought a phone with a bad ESN and wondered if it is possible to fix it
Nope, not legally.
Did they know it was bad when they bought it?
No they didnt
Then I would look into seeing about returning the phone for a refund if possible.
It was a craigslist deal and guy ignores his calls
I am not sure on Craigs list policy with that sort of thing, so I can't help you with what to do to try to get a refund/return.
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