INCREASED WRONG CREDIT CARD LIMIT

I had a call from the Nedbank Call centre last week, asking if I would like to up my credit card limit. So i was like yes sure, as I needed some extra cash this month. So i go and buy some stuff and decide to use my credit card to pay for it, and it went through. a few days later I go to the Nedbank ATM to draw cash, and no funds available! So i went into Nedbank, only to find out the increased my garage cards limit. I clearly remember the call center agaent saying 'credit card limit'. Now i keep getting sms's from Nedbank stating my card is over drawn. I called in to see if they can rectify the problem by now increasing the CORRECT card, and they now wont allow my as my credit card is in excess! Who's fault is this? And WHY did it allow me to go over my limit by R800 odd rand?? AT the end of April I now have a huge amount to pay back including my installments which i cannot afford so please can someone rectify this problem that was caused by Nedbank ASAP. This account would not have been in excess if Nedbank had increased the limit on the right card, and also if Nedbank hadnt allowed for the sale to go through if the limit wasnt increased.