Very poor Telkom!

Despite cancelling my landline account (from my previous property) three times over the last two years, they keep billing me. Now owe R3416,41 and it is affecting my credit record!! No one seems to know how to assist me in getting this resolved?! No logged complaint with ombudsman - I have had enough! The sad thing is that I have 3 other accounts with them which I now want to cancel as well.