A scam which attempts to fool people into thinking a fraudulent caller is legitimate is becoming increasingly common.
'Number spoofing' is a trick whereby fraudsters are able to display a different number on your phone to the one they are actually calling from. This means that a scammer can call you, pretending to be from your bank (or other trustworthy organisation) and the number that appears on your phone will actually be the real phone number of the organisation they are pretending to be from.
The fraudster will then try and win your trust by pointing out to you that they are calling from a legitimate number, so therefore they must be a legitimate caller.
This is the first clue to let you know that all is not what it seems; your bank, the council, HMRC or for that matter any other legitimate caller will never try to convince you they are genuine by drawing your attention to the number they are calling from. If you receive a call in which someone tries to do this, you should put the phone down. At the very least you should be very suspicious and not give away any personal information until you have absolutely confirmed that the caller is genuine.
If you are ever in doubt about the identity of a caller, tell them you will call them back. In most cases, a scammer will then become aggressive or abusive, giving themselves away instantly.
Always make sure that you 'clear the line' by disconnecting the call and waiting a few minutes before calling back, as scammers can keep the line open. Always dial the number manually - don't simply return the call.
According to Financial Fraud Action (FFA UK), number spoofing has become increasingly widely-used. This advice is from their spokesperson, Craig Jones:
Number spoofing is becoming increasingly common and it’s not difficult for the criminals to fake a caller ID. So if a number appears on your phone’s caller ID display, you shouldn’t assume you know where the call is being made from. Remember that if a caller is trying to draw your attention to the number on your phone display, it’s very unlikely the call is genuine as there is no legitimate reason to point it out.”