Horrible Service and Unprofessional

I cancelled my fax line in October 2018 and I received my bill from Retha Swart on 18 December 2018 with a total amount of R592.07 payment till end of December. I did explained to her that my bill was supposed to be cancelled in October and according to the statement send I must pay R259.42 till October and she must investigate why they did not Cancel my fax line. to my surprise today I received an email that I have been handed over to the debt collectors. What the hell is this and very unprofessional and poor service.