He's a "cheeky, funny, super-intelligent monkey" who claims he can answer any question you can think of, from how to dump your boyfriend to what time is the next bus. But Bongo, a UK text message information service that targets young people, is now in a whole heap of trouble after landing parents with mobile phone bills running into hundreds of pounds.

PhonepayPlus, Britain's premium rate phone number regulator, has fined the Australian company behind the service £70,000, and ordered it to pay refunds following complaints from parents. One reported that their 11-year-old had run up charges of £200 after firing off a string of questions to Bongo.

Users of the service – whose website prominently features a monkey image – text their question to a premium-rate shortcode, and then typically receive a reply a few minutes later. But the regulator said some children were unaware that texts cost £2.50 a time because the cost was not made clear.

PhonepayPlus said Bongo was advertised during reality TV shows and at live music events, some of which were largely attended by children, including One Direction concerts. Wristbands that carried the number people needed to text were handed out at the events, but the charges were written on the inside of the wristband in small print.

The fine has been imposed on Bongo Operations Pty Ltd, based in Richmond, a suburb of Melbourne.