To begin with, you should file a police report, explain to the bank what happened, and if they refuse, go with a lawyer. The lawyer will know what to say, but banks have a duty of care; they usually reach an agreement before going to court because they know it's unlikely they'll win in court, and if they lose, they set a precedent.
You could do all that yourself without a lawyer. And it wouldn't be your bank you'd be taking, it would be the merchant on the statement.
Banks are not legally obligated to raise chargebacks, its a voluntary scheme. But they do have a duty of care to act in fairness to all customers.
Given the amount of transactions to various merchants, it could be easy for a bank to prove claimant knew exactly what they were doing.
Lawyer might only tell you any of this after you have paid them.
