How can you stop web game extra charges?
The BBC's Technology correspondent Rory Cellan-Jones explains some of the things you can do to prevent charges from web and phone games.
The Office for Fair Trading is investigating if the games put undue pressure on children to pay for additional content.
Many games ask players to pay to get coins, gems or other virtual items to speed their progress through levels.
Figures gathered by the OFT reveal that the vast majority of the most popular smartphone games were free to install but raised cash for their creators via in-app purchases.