Engineers have had to repair more than 150 phone lines after thieves have stolen copper cabling.
A total of 600 metres of underground cabling, owned by BT, was stolen from the Chalk Lane area of Narborough during the early hours of Wednesday last week.
Openreach engineers replaced the cabling and reconnect the phone lines.
A BT spokesman is urging residents across West Norfolk to report suspicious behaviour around street cabinets and manholes.
He said: “The theft of metal is a continuing problem in the UK, affecting many industry sectors.
“A BT partnership with Crimestoppers offers up to £1,000 reward for information leading to arrests and subsequent successful convictions.
“Network security is of paramount importance to us, and BT uses many security measures in the fight against cable theft, including RABIT technology that alerts police within minutes of a cable being cut, SmartWater, the invisible paint that tags thieves. SmartWater trap devices are also deployed in hot spot areas with thieves targeting BT property facing being sprayed with the liquid.”