Cannot get credit card money back

I tried making a booking on 1st December for place to stay for my December holiday. While making the booking the merchant gave an error and said the bank was unable to verify my credit card detials and the booking did not go through, but the money was still taken from my account and is now in pending state. FNB refuses to help and keep on saying they cannot do a thing. During this time they have had technical issues and I believe if this failure ia their fault due to their technical problem they should be doing more to fix it and reverse the transaction. So no help from fnb after I had to call more that 7time, was transfered arround 5 to 8 times per call and had to deal with a faulty automated verification system. Thank you FNB for a horrible customer service