Account suspended for no reason & I must pay!

My account was suspended on the 2nd of May after I had paid my account already on the 14th April. The store could not help me saying that i need to speak to Credit Control. I phoned customer care and waited 40 minutes for my call to answer. I was informed that I reached my credit limit and that if I want it unsuspended I would have to pay for the promo fees. I don't understand. It is a new month I paid my last bill. My phone is suppose to switch to prepaid when I reach my limit and you want me to pay more or less R100 extra. This has happened twice to me now am I suppose to expect to pay this extra every month when you feel like suspending my phone and I have paid for my services!!! Someone please fix this...this is not what I signed up for. If I have to take this further I will.