Apalling service and customer care

After I have tried several times to get MTN to give what I pay for I gave up and decided to cancel my Uncapped lite package I have had for over 6 years. Call centre took my call and processed the request on 16 October and said I will get feedback by 20 October. Lo and behold, no response from MTN, Today I called 3 times and waited on the line for the retention department for an average of 10 minutes each time, no one picks up. MTN is happy to take my money, but it seems they have fundamental problem in providing the agreed service in return. I just want to cancel a service that has no benefit to me.