Double purchase

I purchase the 50$ pack. In the end of the procedure it sais "you still need to autorize..."
I click autorize and it sais "autorize timed out". No points to spend, it didnt work.
I do it again, now i have 900 points O.o

I want to undo this and get my money back on the doubled purchase. Not back to steam, but back to my credid card. How do i go about this ?