MTN inconveniencing due to their incompetence

I cancelled my phone insurance and thus was confirmed in writing by *** on September 18. For the month of September understably I was billed, however my October invoice should not include the insurance amount which it does and I escalated back to MTN for them to revise the invoice accordingly. Invoice has not been revised, no response from MTN on my escalation instead my phone services have been suspended This is ridiculous to expect me to pay for something I have cancelled and inconvenience me for your incompetence.