The European Commission unveiled an interesting fact: half of 10 year old kids in the EU own mobile phones. This figure reaches 95% concerning all the kids under 16 years old. However parents are still anxious that their children are not protected enough.  

So, Cyprus, Estonia, Finland and Luxembourg don’t have "voluntary" agreements requiring operators to control access to adult-orientated material. In those countries only 41% of operators worry whether those measures are working.

It is also important to make the network operators responsible for the content they provide, even through a voluntary agreement. As that is a problem that offensive content can equally come from other users, rather than from commercial operators. Internet service providers are still not responsible for children protection. Thus, for example porn providers don’t usually want under-age customers as they lack money to pay for the content and they agree with 51% of parents. 

A credit-card authorization is used in most places to make sure the user is over 18. However, that's more difficult with pay-and-go handsets, especially in countries, such as the UK, where there is no identity, and thus age, check when buying a phone.