In iOS, there are several ways to limit in-app purchases.

How to use screen time to prevent in-app purchases

  1. Open the Settings app and tap [Screen Time] . If you have turned off the [Screen Time] , turn it on.
  2. Select the [Content & Privacy Restrictions]
  3. Enable the [Content & Privacy Restrictions]
  4. Select [iTunes & App Store Purchases].
  5. To disable in-app purchases, select [In-app Purchases]>[Don't Allow].If you always require a password when making in-app purchases, select [REQUIRE PASSWORD]>[Always Require].
For other purchase restriction options, please visit this Apple support page.