FNB leaves me stranded in the USA!

I am travelling in the USA and arranged for my Global card to be used to make payments during my travels. FNB decided to block my card leaving me stranded in the USA unable to make any payments. No Prior communication or contact from them at all. Just blocked the card with a one sided decision and no communication about this prior or after the decision. I have contacted the secure chat line but they can't help. Leaving me and my family at risk! They can contact me on USA number ***