Regus Office Space

I had a month-to-month contract with Regus. I have a copy of this.
I cancelled my contract, and have a confirming email.
I was billed for additional months after this date.
I called the billing department. The girl did not understand my problem so I asked to speak with a supervisor. I was told one would "call me back." To date no one has called me, and a few days after my call, they sent me to collections.
What a horrible way to conduct business. I was being pro-active to resolve this problem.