Happens on xbox/ps too. The best way to handle it is to explain to your children how it works and educate them. I allow mine to spend money on Fortnite skins because they know what they are getting and what it is costing. Their cousin, I recently found out, spent £400 on Roblox tat after taking their parents credit card. Now the excuse can never be I didn't know, which is what their cousin said, even though she had taken the card and used the details, as opposed to it already being registered and the child just clicking 'buy' with no awareness.