You need another opinion. That body shop sold you a steaming pile.
They just do not want to accept responsibility.
Go someplace else, AND get a lawyer. Actually call your insurance company. They are the people who paid for the crap job. And usually they can get satisfaction.
I had a repair go bad. And the repair place had that 'get lost' attitude.
The insurance co got involved and the repair place was all over themselves and fixed the issue.