MTN doesn't know the basics of customer service

I want to cancel my cellphone contract. I have been trying for two weeks to get this done. I wasted two hours in the store for them to tell me I needed to do it via phone. I complained on their website and facebook page. I have a customer service reference number. They tell me they have referred it to retentions. I have three reference numbers from retentions. They tell me they will revert in three days. It has now been more than two weeks - nothing happens. No matter where you complain MTN just doesn't care, doesn't respond and doesn't sort it out. I would never have thought that an organisation of such magnitude would do so poorly when it comes to customer service. Absolutely shocking. I have no words