Ofcom* recommends that you should send your ISP a copy of your bill, highlighting the relevant charges and the reasons why they are being disputed. If this fails to resolve your dispute, you should follow its formal complaints procedure. If your dispute is still unresolved, you can raise the matter with the relevant Alternative Dispute Resolution (ADR) scheme.
* Ofcom is the UK communications regulator. For more information, advice and how to complain, visit the Consumer Section of the Ofcom website or call 0300 123 3333 or 020 7981 3040. Lines are open Monday to Friday from 9.00am to 5.00pm. For Text phone: 020 7981 3043.