Bad service!

I did an upgrade on my contract on the 2 March 2015 and asked the lady that did the upgrade to set a limit on my lines she said she did in May 2015 I received a huge bill, I immediately phoned customer care they told me it was a mistake on their side and it would be fixed, it's 5 months later, numerous emails and phone calls and it's still not sorted. My lines are suspended I was told to phone the pre legal department but no answer. This account has been under investigation for months. I pay my account every month but no service I've been a customer with MTN for 6 years this has never happend before. Please sort this out and let pre legal department contact me immediately don't tell me it's been escalated those words mean nothing!