Protection1 False billing! Wichita, Kansas

We had Protection 1 security system in our medical office.  On or about August 19, 2010, we started looking for a new location and sent a letter to Protection 1 stating that we were discontinuing our service with their company.  We informed them that we were moving, and would no longer require their service.  We were informed by Protection 1 that the contract expired in November, and they would continue monitoring our facility until then.  About January of 2011 we received a collection letter.  I contacted the company and explained we were moving out, and we had cancelled the service.  Lucy & Keera at extension 27003 stated We see your cancelation letter and apologize for any inconvenience.  Then about 4 months later we started receiving, letters, and telephone calls attempting to collect on an alleged debt.  I spoke to Stephanie at Protection 1 on or about June 8th and she stated, please fax me a copy of the letter and I will take care of it for you.  So I faxed a copy of the letter to Stephanie.  Then on or about June 29, 2011, Nick from Protection 1 customer service called and said, if we fax the letter to him, he will resolve the issue at hand.  So we re-faxed the information to Nick.  We are now receiving telephone calls daily.  We do not have an outstanding balance with Protection 1, and I want the harassing telephone calls to stop!