A company that charged consumers for "free" text vouchers has been fined £100,000 by the regulator.
PhonepayPlus has ordered refunds for consumers and fined the voucher service Free (b) after it charged recipients without proof of their consent.
The company admitted to the regulator that as many as 30,000 people had been subscribed from a bought marketing list.
Free (b) offered text vouchers giving customers items and services like free entry to cinemas or free coffee.
But PhonepayPlus found that Free (b)'s advertising did not provide consumers with all the information they needed and was unclear about the cost of the service.
The first offer that consumers saw on Free (b)'s website was Get Free Stuff to your Mobile when in reality they were charged £1 for every text voucher sent to them.
The PhonepayPlus investigation found that the company behind Free (b), Moblix Media Ltd, had charged consumers without their knowledge or agreement.
PhonepayPlus received 52 complaints from consumers who had found the charges on their bills.
The regulator's director of strategy and communications, Patrick Guthrie, said: "We found that people were being charged by Free (b) without agreeing to it or even knowing anything about it.
"Under our rules all consumers must give informed consent before they are charged for any service.
"All phone users should look at their bills regularly and check anything unexpected on the number checker on our website.
"Our independent tribunal classed this as very serious and fined Free (b) £100,000."