Chris Williams, telecoms analyst for the independent consumer advice firm uSwitch.com, said: 'If you are approached on the doorstep, don't sign anything at all unless you actually want to switch suppliers. Make sure you take the salesman's name and the name of the supplier. If it's over the phone, don't agree to anything at all unless you decide you want to change supplier. Again, make sure you get the person's name and their employer's name.'