Thousands of hearing-impaired Australians could face a return to 1980s technology from today after the Federal Government cancelled a deal to support text-captioning telephones.

Key points: CapTel phone users have been asked to switch to older technology or internet-based calls

CapTel phone users have been asked to switch to older technology or internet-based calls They say these options are slower and less user-friendly

They say these options are slower and less user-friendly The Government says the rising cost of the CapTel deal was not sustainable

Phones with CapTel captioning display words on a large screen in near real time, so deaf and hearing-impaired users can make calls and see the responses.

But in a decision criticised by disability advocates, the phones will not work as of February 1, after the Department of Communications declined to renew the service provider's contract with the National Relay Service (NRS).

A new company won the contract.

It will force users to take up alternative options, with many choosing to revert back to what are known as TTY teletypewriter phones — technology first introduced in the 1980s.

For Christine O'Reilly, the CapTel phone changed her life.

Ms O'Reilly's hearing has been deteriorating since childhood and now at 62, she is profoundly hearing impaired.

"When I received the CapTel I was so overjoyed I burst into tears," she said.

"I had developed a phobia about using the telephone. CapTel allowed a new world for me."

She said many callers did not even know she was using the device.

"For once in my life I [was] on equal level," Ms O'Reilly said.

"[Now] they're taking away the most inclusive, accessible telephone."

She organised a petition and worked with other CapTel users to try to keep the service alive, but their efforts failed.

CapTel's popularity blows out funding

Critics say the decision has come down to one thing: money.

The cost of the NRS has blown out in recent years, from $26.3 million in 2015-16, to $31.2 million in 2017-18.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 16 seconds 16 s The size of the two phones' display screens are significantly different

Much of that increase was due to the popularity of CapTel phones, which were paid for on a per-minute-of-use basis.

The new NRS contract awarded last June provides for $22 million per year over three years.

Until recently there were more than 3,500 CapTel handsets distributed across Australia. The Department of Communications estimates about 1,000 are still active.

"I certainly acknowledge any transition of this kind is challenging, particularly for older Australians who may not be as familiar with technology," Minister for Communications Paul Fletcher said.

"We've retained a team of trainers who've been going to meet individually with CapTel users to brief them on their alternatives."

Mr Fletcher said he hoped the owner of CapTel technology, Ultratec, could reach some agreement with the new NRS contract holder in the future to resume the service.

It is expected many users will switch to TTY teletypewriter phones, which have a small two-line screen for text above the number pad.

Alex Harrison says the CapTel phone has made it possible for him to run his veterinary practice in Adelaide. ( ABC News: David Frearson )

"We're having to go backwards in time, and everyone else can get the latest iPhone," said Dr Alex Harrison, a profoundly deaf veterinarian in Adelaide.

"[I feel] enormously frustrated and discriminated against," he said.

Dr Harrison said the CapTel phone had revolutionised his practice, allowing him to easily make up to 10 calls a day.

Making a call on a TTY phone is much more complicated.

"If I want to make a phone call on the TTY, I have to call a 133 number first … and they'll put me through to an operator," he explained.

Dr Harrison makes around 10 phone calls a day on his specialised phone. ( ABC News: David Frearson )

Once you do that, you may be put on hold or told you are in a queue to make a call.

On January 7, the department acknowledged wait times to get through were unacceptable.

"We understand and acknowledge community disappointment about these issues and can assure you that we are focused on resolving these concerns as a priority," it said.

To address the wait times, the relay service provider Concentrix is currently hiring and training additional staff.

New staff took their first calls just prior to Christmas and more staff will commence during the rest of January.

Eighty-year-olds told to go online

Other options offered by the Department of Communications are internet-based call captioning and apps designed to work on mobile phones and tablets.

But users said many of the online options were much slower and less user-friendly, requiring them to fill in multiple fields just to initiate a phone call.

"The other options are far too slow. They're primitive," Ms O'Reilly said.

And advocates point out the average age of CapTel phone users is more than 80.

"For an elderly person who's not tech savvy, [these options] can be very intimidating, and often they can't do it. Some of these people are 80 or 90, and they really struggle with that," Dr Harrison said.

Ms O'Reilly said she did not know what she would do when her CapTel phone switches off.

"I'd gone most of my adult life having to get other people to make my calls," she said.

Now she fears losing the independence that comes with ability many hearing Australians take for granted.