Mtn - Takes money without delivering service

Mtn still has not resolved the ongoing issue with them, expecting payment but not delivering as per the terms of the current contract!!! Imagine expecting 150gb day data and receiving only 50! We've lodged at least a dozen queries with their customer service department, and their system shows they've resolved it! How is it resolved when the data is not on my phone!?!? Numerous requests for a manager to phone is just ignored! But if we only pay one third of our bill, Mtn will remember to call unlimited times for their money, yet they don't give a damn about service delivery and accountability! We will not be paying a cent on this contract until this issue is resolved! It's more than half the month gone and I'm sure Mtn expects to be paid at the end of the month, my question is, paid for what??? Mtn, you need to make contact within 24 hours and resolve thus, if you want to see a payment made. Failure to do so means you don't want us to pay. And please hire competent people to work in customer service, who can actually speak clearly, not these people who mumble and are rude with a bad attitude, otherwise you can't call it a customer service department, it's no service received.