BOGUS CALLERS
Wessex Water:
0845 600 3600
British Gas
0845 600 6113
British Telcom
0800 800 150
Sedgemoor District Council
0845 408 2540

Never admit 'Officials' without properly identifying them.
Most large companies (e.g. British Telecom, British Gas, Wessex Water, double glazing companies, etc.) issue their representatives with identification cards.
If they have not made a specific appointment or you are not satisfied that they are genuine, close the door on them and telephone the company they say they represent. No legitimate company will object to your following this procedure.
Preferably use a number from this list or from an advert rather than one your caller gives you.