People in Liversedge and Heckmondwike have reported a bogus boiler scam.
West Yorkshire Trading Standards says people in the area have received calls from an 0161 number offering free boiler replacement and installation services.
The caller, who knows the name of the householder, claims the home has already been assessed and approved for free energy saving measures under a government scheme.
The calls have come to light during Financial Fitness community education sessions, which provide money management advice and raises awareness of scams and fraud.
Coun Andrew Pinnock (Lib Dem, Cleckheaton) said: “Raising awareness of the tactics being used by criminals who are preying on the vulnerable is invaluable in today’s society, especially when scams are becoming more prevalent and evolving often under the guise of genuine schemes.
“For free and impartial advice on how to save energy in your home, you can contact the Energy Saving Advice Service on 0300 123 1234.”