I cancelled an order but how do I get my money back?

Can someone please help me and tell me why to do?

I was ordering an Apple product but as i was ready to checkout, a pop-up that said "oops" came out and made me "re-order." I thought the order didn't go through so i tried it again. The second time was a success.

When i went to check my email for the confirmation of the order, i came across two confirmation numbers. Turns out i was charged twice. i cancelled one order and kept the other one but I haven't received my money back.

It would be great if someone could help me with this problem. Thank You!