Refusing to cancel router

I had two contracts with MTN, but despite my repeated requests, they have refused to cancel one of them. They continue to debit my account for a service that was already taken back, even though I was issued an IRM number as confirmation. Four months ago, I cancelled my home internet contract, yet this month I refused to pay for it since it should no longer be active. In response, MTN blocked the other router that is fully paid and still in use. I have called multiple times seeking assistance, but instead of resolving the issue, I keep being sent in circles without any help.@MTNsa