I once encountered an unintentional payment mishap with In-app Purchases while immersed in gaming. At that moment, I didn't anticipate pressing the payment button to buy virtual currency in the game, and Face ID scanned so quickly. Therefore, I believe it's best to generally disable In-app Purchases for apps. Only enable it when genuinely needing a service or making a game purchase.
To turn off In-App Purchases, go to Settings → Screen Time → Enable Restrictions → Under iTunes & App Store Purchases, select In-app Purchases and check 'Don't Allow.' It's that simple.Once 'Don't Allow' is activated, every time we attempt to make a service payment within any app, a notification prohibiting In-app usage will appear. Unless we go into Screentime to re-enable it, purchases won't go through.I hope those who have faced similar situations as mine can resolve it this way. Taking such action also helps parents managing their children through Screentime to avoid accidental In-app purchases.