Riverina farmers and rural residents want a guarantee from Telstra that they will still get mobile coverage after the 3G network is switched off.
Telstra announced on Wednesday that it would shut down the 3G network in 2024 in order to use its frequencies for new 5G mobile internet technology.
However, farmers say that they are relying on 3G for their mobiles as 4G coverage does not extend far enough from Telstra's existing mobile towers.
Sandigo farmer and campaigner for better rural internet, Lee Longmire, said she was not able to use 4G at her property unless she was near a booster antenna at her house.
"My immediate concern is if they have done correct testing to make sure the signal strength is going to be adequate as they are switching off the 3G service," she said.
"Where I live at the moment, If I try to use 4G outside the house down the paddock or in the sheds, the battery drains extremely fast as it can't seem to get a stable service.
"I have real concerns; unless they can somehow boost the 4G to cover the same area they are going to have to put more towers up."
Telstra posted a message on it support website informing customers that the telecommunications giant would be "switching off 3G in mid-2024".
"While this is still a while away, we're making the announcement now so our customers have plenty of time to change to newer devices if they have a 3G only device, or a 4G device that doesn't have 4G voice calling capability," the statement said.
"We launched 3G in 2005 and it was cutting edge technology at the time.
"We now offer our customers extensive 4G coverage which provides vastly better data speeds and improved customer experience for streaming sport and entertainment and using graphics and video rich social media platforms."
Tumbarumba country music performer Fanny Lumsden said she and her husband still relied on 3G for their businesses at home and on tour.
"We spend our time touring all around the country and it will affect so much because we are doing our business all the time as we go and we rely on (mobile internet) hotspotting off our phones," she said.
"It's already hard to do that in 3G areas but when it doesn't exist it will make it even harder.
"We are using (finance service) Square to do portable EFTPOS at events and it relies on hotspots and often we are in areas where if there was no 3G, there would be no service at all."
Telstra said it would be "repurposing the 850MHz spectrum, currently used to provide 3G coverage, to support our 5G rollout".
"This will let us grow and improve our delivery of next generation 5G technology," the statement said.
Telstra's previously shut down its CDMA network in 2008, which prompted complaints from farmers and rural residents at the time.
Mrs Longmire said her CDMA phone had been "they best we ever owned" and had "worked everywhere" before the network closed.
"It seems like every time they bring in a new mobile network the internet capacity goes up but the range goes down," she said.
A post on the Better Internet For Rural, Regional And Remote Australia Facebook page about the pending 3G shutdown attracted more than 140 comments, mostly about concerns that the 4G network would not fill the gaps.
There were some comments that welcomed the move, hoping that re-purposing the 3G frequencies to boost other services would improve their connectivity.
A Vodaphone spokesperson told the Sydney Morning Herald that the company had no current plans to shut down its 3G network and an Optus spokesperson said they had not confirmed a shutdown date for their 3G network.