2 weeks and still awaiting closure on my query!

We have recently travelled to Botswana by car. We stopped in Gaborone to fill up with petrol, but the attendants said that they did not accept Mastercard as their system was "down" The only VISA card which I had was my Business FNB card which I presented. They swiped and the transaction was declined, they then used another machine and swiped again with the same result. Another attendant mentioned that we can use Mastercard and I presented the card (from another bank) and the transaction went through. I've forwarded all the necessary information and followed up on numerous occasions without much assistance. Eventually I was notified that they have refunded 1x amount, not sure why only one was refunded and not the other? This process has taken more than 2 weeks and it is still not resolved. I emailed my business banker and the person who tried to assist from card division that I need closure, but this fell on deaf ears.