Unable to close land line account

I have been struggling to close my fathers (deceased) Telkom land line account for quite some time now. He passed away in September last year, and Telkom has been billing him ever since. I have been to their stores numerous times,I even tried cancelling the account online! I have also called in to their call center for help but that was useless - after being re-routed to different departments I eventually got an email address that I could use but nothing has been done about it. The service is not being used at all and all I want is for the account to be closed!