Telstra, Optus and TPG representatives were questioned at a federal parliamentary hearing over 3G closures on Wednesday 24 July.

While Telstra claims it's 4G network now has largely the same coverage as its 3G counterpart, business and medical groups told the hearing they are still worried rural Australians will be cut off when the old network closes on 31 August.

The same claim has been made by residents and business owners within the western plains, who believe that the 4G and 5G footprints will not match the current 3G service area.

In a submission to the inquiry, the Royal Flying Doctor Service (RFDS) said many bush areas in low population and isolated areas still rely on 3G to communicate.

"A lack of reliable connectivity, particularly in areas where there are no local health services, can create extreme and unnecessary risk during emergency situations and creates a barrier to receiving telehealth services," the submission said.

RFDS Chief Information Officer Ryan Klose also told the inquiry the service has used alerts which rely on 3G to keep clinicians safe.

"This could be 25-year-old male or female and they go into these strange communities by themselves," Mr Klose said.

"We give them duress alarms powered by 3G, security alarms."

Mr Klose joined the bi-partisan parliamentary hearing via video link. YouTube/ Australian Parliament House Streaming Portal 

Mr Klose said the service has also used 3G across CCTV systems, emergency communications channels and clinician vehicle tracking.

He said the RFDS has so far spent between $150,000 to $200,000 to replace 3G-reliant equipment with 4G or satellite.

Meanwhile, the National Farmers Association (NFF) said ahead of the hearing that it's concerned about "unforeseen impacts" on devices including agricultural technology.

"While we acknowledge the opportunity the shutdown presents to improve connectivity across the country, farmers and communities are understandably apprehensive about what a world without the 3G network means for them, an anxiety made worse by anecdotal reports of degrading and changing mobile service in some areas and a general lack of confidence in existing complaint processes," an NFF spokesperson said.

Telstra representative Gerard Tracey at the hearing in Canberra. IMAGE: YouTube/ Australian Parliament House Streaming Portal

Telstra Principle Engineer at its Network Connectivity Service, Gerard Tracey, told the hearing it has been working towards a point where it's 4G network covers the same areas as 3G, also referred to as "coverage equivalence."

"The way that we've gone through to confirm coverage equivalence is, as we've built out the 4G network, we've done drive surveys, we've done analysis of call records, we've actually done independent surveys to go out and validate that this coverage point 3G and 4G network is equivalent."

Optus will also begin shutting down its 3G network from September while TPG, which owns Vodaphone, pulled the plug in January. The network was introduced to Australia in 2003.

Ahead of the deadline, Telstra has sent messages to customers with devices that are not 4G compatible. Customers can also check compatibility by texting '3' to 3498.

Telstra has an online interactive map showing areas it says are covered by its 3G, 4G and 5G networks.

However, Coonamble business owner Lucy Moss said 4G doesn't reach her home kilometres north of the town and has trepidation about the impending 3G shutdown.

"It's something that we've been aware of for a really long time. In their defence, it hasn't been a sudden movement by any means, however I think the criticism comes back to the fact that what they're replacing it with just isn't adequate for us," she said.

"At the moment, the 4G cuts out pretty much within a 20-kilomtre radius around town."

She also has a signal booster in her car which only works with 3G.

Telstra Chief Sustainability Officer Justine Rowe said the service provider will work with customers where they report discrepancies in service on the map and on the ground.

"If a customer does have a concern we welcome them contacting us and we will work with them understand the concern, what's actually driving the experience for that customer and how we might be able to support it," Ms Rowe said.

"That will happen post-closure."