Regulator PhonepayPlus has issued new rules to control the premium-rate services offered for mobile phones in the UK.
The rules, that will cover such services as ringtones and downloads, are an attempt to stop rising complaints about the £350m-a-year industry.
To protect consumers, especially younger users who are more likely to fall foul of hidden charges, the regulator has ruled that subscription services must generate a free confirmation text message detailing the costs and conditions.
In order to be charged, the customer has to confirm their subscription by replying to the text.
Other measures include licensing for service providers, prices must be displayed clearly and customers should be able to end the subscription by texting STOP at any time.
Acting chief executive of PhonepayPlus, Paul Whiteing said: "Consumers should not need to work hard to understand the full price of any service".