Account Locked/Suspended Unfairly

My Vodacom account with 2 lines, one on Uchoose100 and the other on SmartS, were suspended due to credit limit reached. I normally pay a combined bill of +/- R800 every month. Vodacom then decided to reduce my credit limit from R6000 to R1000 in February 2015. On the 5th of February 2015, when my bill was still +/- R400, Vodacom added a proposed invoice of +/- R800 to my account. This, in Vodacom's system, was interpreted as if the account had a balance of +/-R1200, which was above the new credit limit and subsequently suspending both of my phone lines. The customer care call centre referred me to Accounts Department who said they cannot help me and if I wanted my lines to be re-opened I have to make a pre-payment to my account in order to reduce the balance, even though my account was not in arrears and still have the free minutes on the SmartS and airtime on UChoose100, failing which I had to wait for the end of February when the amount on my account becomes due and the normal debit order is run.