EE - Mobile Guide to Mobile Phone Safety – https://ee.co.uk/help/help-new/safety-and-security/content-lock/set-up-safe-manage-childs-phone
This section of the EE website has useful advice regarding mobile phone safety for parents.
If you want to report material you believe may be illegal, contact;
Internet Watch Foundation (IWF)
5 Coles Lane, Oakington,
Tel: 01223 237700
Fax: 01223 235870/921