Should have Reported the phone as stolen, then when they try to sell it , they get  arrested as they have said they returned it to you.

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@Anonymous wrote:

police will only say its a CIVIL MATTER and action fraud are useless

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Maybe that's why they have now changed their name to Report Fraud?

In all seriousness, they don't have the resources to act on every report they receive so will only actually do anything in very serious cases or once a sufficient number of reports have been received against a particular individual to make it worth their while.