MTN's really poor service

I had a cellphone contract with MTN for 24months now and I thought when the 24months period is over they will automatically cancel it. They didn't, so I went to their nearest branches in Durban masgrave mall and Pavilion mall to cancel my membership with them, the service was really poor I didn't even get assisted, they told me I should dial 135 on the MTN Sim card of which I did. Clearly they were just saying this to brush me off. I tried to dial the number 135 and it didn't even give me options to speak to a consultant. I visited all their pages on every social network they have to enquire about this and got no response or any assistance. I am really ****ed off and so disappointed with their service. I don't want to block it from my bank side first before knowing it was cancelled on their side to avoid a bad credit score on my name.