Unauthorized Monopoly game charges from Apple

You have authorized your child to make purchases when either giving them the Passcode to your device or using a Family Plan that authorizes them to make purchases to your card. Apple does provide many methods to prevent a child from making purchase if that is what you want to do, but they must be used by you.

• Request Password for Purchases

Require a password for purchases in the App Store and other Apple services - Apple Support

• Prevent in-app purchases

Use Screen Time to turn off in-app purchases on your iPhone or iPad - Apple Support

• Ask to Buy - Approve what kids buy with Ask to Buy - Apple Support
• You can even remove the App Store, so no apps can be downloaded by going to Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > Installing Apps. Change that to Don't Allow and no apps are able to be downloaded.

If the child signed up for a subscription, then you can cancel the subscription by going here:

If you want to cancel a subscription from Apple - Apple Support