That's a fault in the company's management and SOPs, not yours as a trainer- plus they pick someone who they don't think does a good job in the first place?! Idiots. Also your boss can go **** himself.

For a brief moment you were in the position that most of us only dream about.

I really hope you hung up on that asshole.

after firing you, your old boss has no business calling you to bitch at you. it's no longer your problem. screw him

Yay capitalism!

It sounds like you had no warning that you were about to be fired, and sneakily tricking someone into training their replacement is incredibly douchey. Not giving you a chance to fix your mistakes (if any) is douchey. Calling someone to complain that they didn't train someone to do better than they did...after firing them...that's shooting-into-andromeda level douche.

Please tell me you told them to eat a dick when they called you to complain

should have yelled back and said good for you.

Say, "**** you," storm out, and never come back.

He wasn't the boss of you. You did not have to listen to his shit.