Hey Sha Yi,
I'm Ann, from the team here at Shopify :)
It can definitely take a couple of days once we receive all the information in order to process a refund. What needs to happen is we gather all the information from you, and send it to our Billings team, who then reviews the information and makes a decision on whether or not we can issue the refund. In those cases, no matter what, we will always reach back out to you through email to let you know the outcome- so you'll always hear back from us as soon as we can get to the bottom of things.
That said if you feel like you've been waiting too long, feel free to reach out to us through any of the methods on this page, and we can see if there's any update to share with you :)
Have a great one,