Removing Boost add add ons

[CourantRobbins]

I have a mobile contract for my son, with  a basicl plan of £10/month that is enough to get in touch with me. The problem is that if he runs out of data (about 8GB) he goes to his Three mobile app and purchases a Boost add on that is billed to me.

How can i disable buying add ons from his three app.

[MZone]

Not aware of anyway to stop this unless you change the password to the 3 account and manage it so he can’t log into it and buy one himself.