Overcharged on my Credit Card

On the 21st of February I swiped my credit card for two envelopes sent to other African countries amounting to R680.00. All of a sudden I received a call from my bank, FNB on Monday the 18th of March stating that an amount of R136, 097.00 was taken from my account on the 16th of March by DHL International and asking me how am I going to pay back this money as I have only a limit of R5, 000.00 on my credit card account. I was gob smacked first and foremost surprised as this is a question to FNB actually as to how could they allow my bank account to be debited for this amount even though I only have a maximum limit of R5, 000.00 on my credit card account? When investigating my statement I realized that the amount of R680 never went through on the 21st of February, instead they debited my card almost a month later with this amount. Since then I have tried to get clear answers from both FNB and DHL of how this happened, but more than 10 days later and I have not accomplished anything. I just wish I can get some answers and an apology as this is causing huge distress on my end. I cannot use my card, who is going to pay for the interest on this huge amount outstanding ,what about my credit record etc. I reported this to the FNB ***** division but it seems it does not get sorted out. Believe me, if I want to spend so much money, I would not spend it at DHL and probably buy a car rather or four lavish overseas vacations. Truly very disappointed with FNB and DHL as we have to phone all the time to follow up and nobody seem to be sorting this out