Police received 21 silent phone calls from a man in Wisbech who was trying to unlock his phone.
Officers were sent out on blues and twos to the property after the calls were received in case the man dialling was facing an emergency.
However, on arrival they discovered that the man was actually trying to unlock their phone as it is stated online that if your mobile phone is locked, calling 999 would unlock it.
A Cambridgeshire police spokesperson said: “We do investigate every silent 999 call to ensure someone is not in trouble.
“However, 999 should only be used in a genuine emergency - and not to unlock a mobile phone.”