CANCELLED LINE 13 MARCH 2018

I have been your customer for the last 6 years having a telephone line and a ADSL Line. I have recently gave notice to cancel my account on the 13 March 2018 which should of been cancelled on the 13 April 2018. I have phoned your billing account center over 10 times now with no avail to helping me which only they say they will escalate it to the person cancelling my line and that the process is stuck. The last person i spoke to her name is Mellisa from the billing account department was so rude and arrogant on the phone she just wants to pass me off to a complaints department that doesn't even exist when calling. I have recently got an invoice from you guys for R1153.45 for this account what is going to happen?? I cant keep paying for this service as ive said that ive cancelled over two months ago, i have cancelled my debit order from you guys otherwise ill be kept on getting deducted but now im scared eventually you guys will black list me because of imcompetent people that cant do there jobs to cancel this account. The last reference i got from that rude lady Meliisa was ********** 59A my telephone line number in question is ********** 405 my contact number is : ********** 234 . Mario Caldeira