Superflex - Absolutely no use

I have a Superflex 10g deal with MTN. It has worked perfectly since we first had it. Sadly since 5 weeks ago, it has not worked. The data line works but voice calls do not work. I have phoned repeatedly to your prepaid department and have not been assisted at all. Various promises have been made, escalation after escalation and still absolutely fix. Sadly to say this is why Vodacom will be the best service provider in South Africa. They know how to respond and give excellent service. I still have to pay my subscription! Not fair MTN not fair