FBB Blacked Online Payments and cant get hold of them to sort it out.

I tried to make make a payment from a website system that I use and the payments where rejected. I then tried a smaller amount and that went through. On the Monday morning I tried again and was blacked again and FNB even put a soft block on my card. I then tried to phone FNB and was told to phone the ***** line but could never get through to them. This is a very important business transaction and can't continue with my work.