Broadband engineers were menaced after false claims spread that they were installing 5G technology in south Armagh.
Conspiracy theories have wrongly linked the coronavirus outbreak to the network.
While any suggestion of a link has been dismissed by scientists, a series of mobile phone masts have been set on fire in UK cities.
The Communication Workers Union (CWU), which represents thousands of workers, said around 120 cases of abuse have been reported.
Andy Kerr, the union's deputy general secretary, said workers had been threatened with violence and even murder.
At the weekend Sinn Fein MP Mickey Brady said some broadband workers had reported being abused.
He said 5G was not being installed in the Newry and Armagh area, and told people not to harass or intimidate engineers.
He said: "We have been contacted by local people who raised concerns over reports that 5G was being installed in the area amid false rumours regarding its impact on the current public health emergency.
"Following consultation with broadband providers we have been assured there are currently no plans to install 5G in the area.
"There are also no planning applications for any 5G infrastructure lodged with Newry, Mourne and Down District Council.
"Some broadband engineers have reported being subjected to abuse while carrying out essential work to maintain the existing network. Such abuse is wrong and needs to stop.
"All workers should be able to go about their work free from fear, harassment or threat."
Earlier this month Economy Minister Diane Dodds expressed concern at "false claims" linking the coronavirus outbreak to the rollout of 5G.
Twitter has also announced it will remove posts encouraging people to take action against 5G masts as part of wider efforts to double down on dangerous "unverified claims" on the platform.
The social network said it has broadened its approach, focusing on accounts inciting the public to engage in harmful activity which "could lead to the destruction or damage of critical 5G infrastructure, or could lead to widespread panic, social unrest, or large-scale disorder".
Earlier this month Ofcom revealed it had received 419 complaints about remarks made by Eamonn Holmes on ITV's This Morning. The Belfast presenter appeared to cast doubt on media reports refuting the myth that 5G causes the virus "when they don't know it's not true".
The following day Holmes said there was no link, but that many are "looking for answers and that's simply what I was trying to do".