Police and Trading Standards are warning members of the public to treat cold calls relating to home security with caution.
Over 30 incidents were reported to the police in June.
The calls came from withheld numbers and some of the callers claimed to be from Dorset Police, which is "not true" according to the force.
Debbie Oldfield, from Dorset Police, said: "These calls seem to be targeting older members of our communities."
She added: "A number of the calls have specifically asked the residents if they are over the age of 80 - and if the resident has answered that they're not, the caller has hung up.
"The callers are reportedly asking residents about home security issues and alarm sales.
"I would encourage all residents to be wary when receiving these types of calls and advise them not to give out any information about security concerning their homes."
Andy Shimmen, trading standards officer for the Borough of Poole, said: "There are many honest companies out there so if you do need an alarm we would suggest shopping around for the best deal and not to pass any information to cold callers or doorstep sellers operating like this."