What can I legally do if a collection agency remove funds from my account without final authorization?

I gave them my account information based on the verbal agreement to give them a lump sum of money on a certain date. The money I thought I would receive fell through so I put a stop payment on the amount I told them I would pay which was 1900.00. They waited a month and removed two hundred dollars from my account. I did not authorize them to remove the 200.00, as I wouldn't talk to the collector anymore over the phone because she was demanding and harring me. Legally, could they remove the 200.00 without my approval.