Bad Service

I went to Safari Now website and I requested a quote for accommodation in Durban, which I received and I accepted the quote, made an EFT payment for R1000 to their Nedbank account as a deposit and I was also using Nedbank account. The next morning I received a message and email saying unfortunately my booking were cancelled. I receive a call from Natalie and she told me the other person was using a Credit and it went through immediately that's the reason why my booking was cancelled. How do the let people to confirm 2 same booking and accept payment from both is their system not showing that someone have accepted the booking. I emailed SafariNow today requesting a refund and I was told it will take 5-8 days for me to receive the refund, when I asked Natalie tells me is not SafariNow fault but the establishment it works on 1st come 1st serve but I paid so I don't get it why should I be told by the establishment working on 1st come 1st Serve. This is so annoying