The Island's telecoms regulator says it's issuing new guidance to companies to stop fraudsters using fake phone numbers.
The Communications and Utilities Regulatory Authority has been investigating potential problems with Calling Line Identification - the number that appears on your phone when someone calls you.
It 's concerned conmen are using fake numbers which aren't made clear to consumers.
After holding a consultation, it says it'll put a new condition on licences for business from next year to make sure they're tackling the issue.
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