Ofcom's advice on your next step

Problems with your internet service -
Internet service bill and contract issues

If you have dial-up internet access - using a modem connected to a telephone socket to dial your internet service provider’s telephone number for each internet session - then you may have unintentionally downloaded what’s called a rogue dialler onto your computer

A rogue dialler is a piece of software which is installed on your computer without your knowledge, usually when you open a spam email or visit a website which contains hidden malicious software. The rogue dialler software deletes the dial-up phone number used by your internet service provider. These dial-up numbers begin with 08 and are either low cost or freephone numbers. The rogue dialler then replaces that number with an expensive premium rate phone number (beginning 09).

There is special software you can install to protect your computer from rogue dialler programs. Please contact your internet service provider for details. You should also make sure you have anti-virus software installed and that you keep this up to date. Your internet service provider may also suggest that you install a piece of software called a firewall which can also help protect your computer from threats on the internet. Some of the software you need is free from the internet, while other programs can be bought in any local computer shop at relatively low cost.

If you have broadband instead of dial-up internet access you should not be affected. Broadband connections work in a different way and cannot be changed by rogue dialler software. However, you should still install anti-virus software (and regularly keep it up to date) and a firewall, as explained above.