"Despite all the technologies that have launched in the last five years, SMS [short message service] is still the leader," says Graham Brown, chief executive of W2F. "We still see pockets of users where younger people are sending up to 50 text messages a day. It fulfils all their needs and it is very easy to use."

Much to the chagrin of operators keen to see early adopters of mobile technology hooked on more lucrative functions, such as picture messaging (MMS), mobile music and mobile internet, teenagers are keeping things simple - and cheap. As Brown says: "One of the problems with the industry is it believes faster is better and that isn't always the case."

In the US, for example, young viewers of the latest series of television talent show American Idol registered more votes by text message than over the telephone, and in the UK, teenagers are sending more text messages every year, reaching a projected total this year of about 22bn.