Refunds are a hassle

I tried to make an online booking, which didn't go through on my side. So I tried again the next day and it wenr through with an email confirmation. I ended up not getting the cars which I understand the cancellation penalty applies but the issue is I was charged twice. I have called their call center more than once (it takes about 20 mins to get through to them by the way) to get assistance and when I finally do I am told I have a double booking and there is nothing they can do. Why wasn't there an email to prove the first booking? I am disappointed.