One elderly victim suffered complications of a mini-stroke during the incident due to the stress.
Leicestershire Police have issued a warning after a number of elderly people in the Hinckley area were the victims of fraud.
Seven reports have been received since the beginning of March where victims, with ages ranging from 71 through to 89, have been contacted by someone claiming to be a police officer from the London area.
In many cases, the victims have been asked to purchase high-value jewellery or gold and then send it to the scammer to prove their card details.
Due to the banks intervening, of the seven reports received four of the victims did not hand over any money or goods to the fraudsters.
Nicole McIntyre, Economic Crime Unit, said: “They should be advised that police officers would never contact them in this way. If they are called they should disconnect the call straight away and report the incident to the police using another telephone, as on some occasions calls can remain connected."
In one recent report, an elderly victim suffered complications of a mini-stroke during the incident due to stress.