Usage limit not removed after 2 weeks

I upgraded my cellphone and 2 weeks ago I got a notification during a call stating that my airtime is low. After a minute the call was cut. Now I am not able to make anymore outgoing calls. I phone 808 and the consultant explained that there was a usage limit of R250 set on my contract. I was never advised that this would be the case when I upgraded the contract and asked the consultant to remove the limit. She confirmed that she has instructed the network to remove the limit and I will be able to use my phone properly again within the next 24 hours. The phone worked correctly again but a week later the same problem started again. I have now called MTN several times and every time I am told that there is a usage limit and it will be removed. I also went into the service center at century drive in CPT where they logged the issue. I made the last call this Saturday (12/09) and was now told that I have to wait 7 working days for this to be resolved. This means I cannot use my phone for outgoing calls for another 7 days. That is not acceptable since I use this phone for business and I expect this to be sorted out immediately. The reference numbers provided are *** and ***