Exceeded Credit Limit

I've been an MTN 3G customer for almost 3years. My account has been suspended as I've exceeded my credit limit. I stopped at the MTN store (14 April) to find out the actual amount and payment options. I was told the invoice is still unbilled and to call back the next day. Called the helpdesk (15 April), after 12 dropped calls and over an hour on hold I eventually got to a consultant who confirmed the amount to be over R3200 whereas the limit I request and is set to R1096. She also advised that the invoice is still unbilled an I should call back today(17 April). Called again with the same experience of dropped calls and extended hold periods!<br> My major concern here is that I've set a responsible credit limit on the account, R2000 over is a huge amount before capping. furthermore, no alerts are sent to the account until the credit limit so I as a customer have no way of confirming when my bundles depleted or that I'm on out of bundle rates. Also my average spend has never been more than about R500 over the monthly bundle. I understand the possibilities of the extra data use, however I have a credit limit to ensure this account is managed.