confidence trick 
(North American confidence game)
noun
An act of cheating or tricking someone by gaining their trust and persuading them to believe something that is not true: they were the innocent victims of an elaborate confidence trick...
- The victim of the confidence game refuses to believe that he is being relieved of his money and dignity, but an ignominious fate awaits him every time.
- He asserted: ‘The whole arrangement is nothing less than a confidence trick perpetrated by the Government against people.’
- In the absence of a supportive fundamental backdrop, a ‘strong dollar’ policy is in reality nothing but an elaborate confidence trick.