Telkom still billing for cancelled line and threatening blacklisting!!

I cancelled my ADSL line at the end of January. I am still being billed despite many follow-up calls to 10210 between April and July 2018, and need to be refunded R620 that was debited after the cancellation period. All the consultants I spoke to assured me that the cancellation would be processed and the account closed withing 7 days. I was given a reference number ( ********** 5) on 21 June 2018 and have heard nothing since - still receiving bills now over R2200 and 3-4 sms's a day with threats of blacklisting and legal handover!!!!! Please can Telkom process cancellations properly and treat ex-customers fairly!