"I think the bank has made an error."
They have lodged a complaint with the financial services ombudsman.
A Commonwealth Bank spokeswoman told AAP the Quiltys did not "strictly" meet the terms of their agreed payment plan.
"We do however acknowledge the customers are genuine in their attempts to meet this agreement and we are working with them to provide additional assistance to rectify the situation," she said.
Mrs Quilty says they received a letter from the bank on Friday saying they had seven days to either vacate or pay the bank almost $600,000.
"Any failure to comply with the demands will mean our client will be left with no choice but to take possession of the security property," the letter said.
Ms Quilty says the bank only contacted them after the media made inquiries on Monday.
She says they fell four months behind in repayments last year after her husband's floor covering business lost its biggest client, whose Rocklea warehouse went under in the Brisbane flood.
Six months after the flood, the couple received a default notice from the Commonwealth Bank.
Mrs Quilty says her husband found work and by the end of 2011, they had paid all arrears by the agreed deadline and have since kept up with repayments.
"I'm shocked. I honestly don't know what's going to happen," she said.
"I don't know where we'll go. We don't have family here but we do have friends.
"But it's not just our home we'd lose, it's also our workplace. We run our businesses from home.
"This could bankrupt us."
-AAP
