Customers of a Sydney plumber have levelled further extraordinary claims at the business after it was accused of overcharging a WWII veteran more than $30,000 for a troubled toilet.

Veteran John Rose revealed on Wednesday he had been quoted $37,000 by Dan’s Plumbing — also known as Ferguson’s — for a “gurgling” toilet and since telling his story, more complaints have poured in about the Sydney plumbing businesses.

One new complaint, from a man in his 90s who suffers from dementia and his daughter, alleged the family was quoted tens of thousands of dollars to fix a problem.

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A disabled retiree was another to level complaints at the now-suspended plumbing business.

NSW’s building commission has since suspended the company’s licenses as it investigates the alleged overcharging.

“It’s absolutely dreadful, absolutely disgusting,” one victim, John Pace, told 7NEWS.

John’s daughter, Jane Pace, said her parents both had dementia and were deeply rattled by Dan’s (Ferguson) Plumbing.

Jane was the one who made contact with the plumbing company after finding them on Google.

“I had a phone call from their office asking to pay a 10 per cent deposit, which I wasn’t aware I had to do,” she told 7NEWS.

“I paid them a 10 per deposit of the quote and the quote came in at $1,400.

“I said, under no circumstances, do not engage with my mum and dad, they have dementia.”

Jane said the plumber later rang her back and said that her parents’ deck needed to be ripped up as the plumbing had cracked, quoting her $16,000 to fix it.

The plumber suggested a payment plan.

Luckily, Jane’s husband’s friend was a plumber, who was happy to come out and give a second opinion on the expected costs of the cracked pipes.

He said there was no reason why the plumber had quoted her $16,000.

Jane ended up paying $550 to fix the plumbing issue.

“They can’t continue operating like this ... especially (with) the elderly and the vulnerable,” she said.

Despite telling the plumbers to not engage with her mother and father due to their dementia, Jane said the plumbers were going to their front door asking for cash to pay for the job.

The couple’s carer stepped in to stop the request.

“They were at the door and they were intimidating mum and dad trying to get this extra money of the $1,400 quote from them,” she said.

“Mum was really distressed. Dad was absolutely so confused and really upset.”

Karin Lewis, who lives with a disability, also spoke to 7NEWS, revealing she tragically forked out almost $45,000.

“I was watching Channel 7 News and the lead-up came in about a plumber company that was cheating people out of astronomical amount,” she said.

“When they mentioned the word Ferguson’s Plumbing, I thought, ‘oh, my God’.”

Lewis had a nasty motorcyle accident in 2016 that resulted in her suffering from short-term memory loss.

She also badly broke her leg, leaving her permanently confined to a wheelchair or mobility scooter.

“I noticed one night that my toilet was gurgling,” Lewis told 7NEWS.

“I looked up plumbers and I phoned one that had already done work at my home, Ferguson’s Plumbing.

“They came out and allegedly put the camera down and then turned around and told me it wasn’t a blocked toilet.

“My sewage pipes were smashed because of a tree that was beside the driveway.”

Lewis said Ferguson Plumbing initially quoted her $31,000 for the plumbing work.

She didn’t get a second quote, thinking it was an plumbing emergency, only for them to add further costs onto it.

“I just thought, okay, I’ve got to get it done,”she said.

“I can’t have a blocked toilet.

“So I agreed to the over $31,000 bill.

“Then they (added) another $8,500 to realign the pipes.”

Lewis doesn’t know if she will get all her money back, but said she felt betrayed.

Dan’s and Ferguson’s Plumbing trade under one company called Australian Trade Pty Ltd.

On Friday, the parent company’s owner tried to overturn his company’s 60-day suspension, issued by NSW’s Building Commission, arguing it would impact customers.

“Taking us out of the industry with no notice will have an impact on consumers,” the owner, Charbel Alha’s, barrister said.

“3765 Of the 3830 reviews for Dan’s Plumbing were five stars.”

A member overseeing the tribunal told Alha’s barrister there were 62 complaints about his client’s business.

The business remains suspended, with a court deciding on the temporary ruling next week.

7NEWS contacted Dan’s Plumbing on Friday, with their operator still taking bookings, not acknowledging their business has been suspended.

Ferguson’s Plumbing is a name used by Australian Trades (Pty Ltd), which also operates under the following eight company names: Andersons Plumbing AUS; Bob’s Plumbing NSW; Dan’s Electrical AUS; Dan’s Electrical NSW; Dan’s Plumbing AUS; Dan’s Plumbing NSW; Lloyd’s Plumbing and Gas; and Willson’s Plumbing NSW.