I want a refund, please

https://support.xbox.com/en-US/games/game-titles/minecraft-marketplace-faq

I didn't receive the Minecraft Coins that I purchased. What should I do?

If you purchased on your Windows 10 device:

Sign in at account.microsoft.com and check your recent purchases.
If you see a completed purchase, restart your device as it may need to be updated.
If you have another Windows 10 or Pocket Edition device, sign in on that device to see if your purchase appears there.
If the purchase appears, there may be a problem on your device. Make sure that you’re signed in with the same account used to complete the purchase.
If the purchase doesn’t appear, contact Xbox Support.

Additional support:

If you purchased from Apple Store (iPhone or iPad), go to the iTunes Store.
If you purchased from Google Play Store (Android), go to the Google Play Store.
If you purchased from Kindle Fire or Kindle Fire TV, go to the Amazon Store.

Additionally all Minecraft Coin purchases are final