Incorrect Billing resulted in Account Suspension

In November 2015, I upgraded my contract with MTN.<br> Since then, they have been billing me incorrectly. Every month I call to contest the billing, and every month I am forced to deal with a different manager who temporarily assists and assures me this will not happen again.<br> This month, I had to call yet again. I spoke to a manager who assured me that he is mailing all relevant documentation to his computer so that he can contact the billing department to get things sorted, after which he will send me a mail.<br> He did not do this.<br> I have been trying to get through to a consultant at the call centre for days now, but I just stay on hold.<br> MTN has now suspended my outgoing services.<br> This really is ridiculous! Why should I have to call EVERY MONTH when MTN is at fault?<br> I want this to be escalated to a higher level now. I can not call every month for the duration of my 24-month contract because their billing department can not do their job.<br>