Android, Web and Chrome App: You can get a refund by going to Menu → Settings → Support → Report a bug. Attach your payment confirmation email so we can look at your order details and proceed with the refund.
iOS & Apple: To be refunded, you need to go through the iTunes Store to do so.
Here are the steps through the iTunes Store:
Launch iTunes on either your Mac or PC.
Click on the iTunes Store button if you aren't already in it.
Now click on your email address and enter your password. If you aren't signed in at all, you'll see a general sign in option.
Once you've signed into your account, click on See All under the Purchase History section.
Here you'll see lists of different iTunes invoices. Find the invoice that contains the item in question and click on it.
Click on the button labeled Report a Problem.
Next you'll be taken to another screen that shows the same batch of apps in that invoice. Click on the Report a Problem option next to the specific app purchase in question.
You'll now be routed out of iTunes and to iTunes Support on the web. Simply sign in to your Apple ID that you use for iTunes purchases one more time.
Here you'll see another detailed list of apps that you've recently purchased within the past 90 days. Click on Report a Problem one more time next to the app you're trying to get a refund for.
From the dropdown, select the reason you'd like a refund. There are several options from you not authorizing the purchase to accident purchases. Put any other pertinent information into the text box and hit Submit.
Please note that monthly subscription purchases are eligible for a refund if requested up to 48 hours after the time of the purchase and yearly subscription purchases are eligible for a refund if requested up to 14 days after the time of the purchase.