First Alert PC Inc Harrassing calls and emails for fraudulent billing for business listing never ordered Westmount Quebec Canada

This company, First Alert PC Inc keeps calling and faxing our office claiming we ordered "yellowphonepages.com advertising.  We did not.  We have ads posted through AT&T for the real yellow pages and they also keep asking for a person that no longer exists.  The person they ask for has not been with our company for many years and has since re-married, has a new last name and moved to another city working for one of our vendors so I am in touch with her on a daily basis.  I have seen others report this scam and have read where they will claim to have a recording of someone ordering this service but when asked to hear the recording, non exist.  They have been told repeated to stop calling, that I am aware that this is a scam and today we received a fax threating to use an outside collection resourse.  They really need to be stopped.