Only IRS (and in some cases Student Loans guaranteed by federal agency) has the power to enter into bank account.  No one else is authorized to do this. 

There may have been some clause in the Credit Agreement that you need to read.  If you can't find it, call the credit card company and ask why this event has happened.  Tell them that you were not provided with a disclosure.  If they don't understand, send them a legal fax (usually few clauses from Lexis Nexis or West Law) and have fun.  If they want to F with you, then go to Attorney General's website and file a complain with consumer affairs.  After that, they will like to have an opportunity to talk to you and settle with you.

Good Luck!  These things are very simple.  Do NOT ever get intimidated with these types of events.