Impossible to cancel MTN contract

I keep paying for a cellphone account I do not use. And it seems impossible to cancel this.

I have send emails to MTN requesting for a cancellation. But as expected with MTN there was no reply or feedback at all. I have phoned customer care where I get to tell the operator I want to cancel my contract and then they say I must speak to another department (retention I think). They then transfer me to that department and after many half hours and even over one hour of holding the phone is just not answered at all. Many times I had ran out of airtime while hoping for someone to pick up since I use another network. It is very shocking that for such big boasting company like MTN you have to hold literally for hours with no one picking up.

I want this account to be cancelled today. Please. If not this is written notice that if not cancelled I will stop paying each month and refer to this complaint should we take the matter to court. I am ready for that.

Don't give me the 30 days notice thing because much more than 30 days ago I send mails and tried fruitlessly to make contact.