What can I do if an Internet vendor took unauthorized money out of my account?

An internet online store made and unauthozed debit from my checking account. I have dealt with this vendor for 2 years. What can I do if they refuse to credit the money back plus any overdraft fees incurred.
What can I do if an Internet vendor took unauthorized money out of my account?
I had the same sort of problem. Report it to your bank. Mine put the money back into my account, tracked down the people that owned the online store and prosecuted them. If your bank won't do this you should at lest put a freeze on your account and get a new account number and never use that store again.