What should I do if a business credit card was opened under my name “by accident” by a bank representative?

Like any thing in life of such nature. You report it. In writing, and involve someone with a legal background.

In your defense you need to show that there was plenty of communication from your end to bring the matter to the attention of the bank for immediate remedial action.

You need to keep writing/communicating with them (online and offline) and keep records of such communication. Make your case stronger. Write every day if you have to.

Fax it to them. Let them know in clear terms, this error / accident is on them. Not you. And you reserve your right to file for additional claims as a result of this accident.