New Zealanders are being cut off from access to free public healthcare in Australia after applying for a change of visa.
Several expatriates told lobby group Oz Kiwi they had had Medicare cards revoked, including one case of an autistic boy suddenly denied a card.
New Zealand citizens are legally entitled to Medicare, whatever their visa status.
In Brisbane, Cameron Forbes-Hood's family was told in January his bid for permanent residency was being turned down on health grounds due to his autism.
In April they got a letter saying the 13-year-old's Medicare was being cut as his visa status had changed.
His mother, Nicole Forbes-Hood, 38, said that even after authorities admitted this was wrong, the battle went on.
"I got on the phone to both Medicare and Immigration and got shunted from one department to another.
"I had operators at Medicare try and tell me that rules had changed in February of this year and New Zealanders were no longer entitled to Medicare.
"I guess if I didn't know my rights I possibly could have gone away and thought, hmmm, maybe there has been changes," Ms Forbes-Hood said.
Eventually she got a temporary Medicare card issued for her son - but with it came temporary cards for her and her husband, even though they both have dual citizenship.
Confused, and with the teenager due for an MRI scan meant to be covered by Medicare, Ms Forbes-Hood went to her local MP who cleared things up.
Gold Coast resident Alex Richards also had her Medicare card stopped in March.
Medicare told her it was because the Immigration Department had rejected her application for a permanent spousal visa.
"Immigration didn't know what Medicare were talking about," said Ms Richards, a 25-year-old state government employee from Upper Coomera.
"So I went back to Medicare and when I asked for their reason for refusal in writing, they promptly phoned me and said that they had made a mistake, and that they had made the same mistake with a number of people, and reinstated it [her card], but I never received anything in writing about it."
She said she feared others less assertive than herself might just roll over and lose the free medical care access.
Complaints point to 'larger problem'
Oz Kiwi deputy chair Joanne Cox said she suspected wider data-sharing between Immigration and Medicare had triggered an an error - but one that was proving hard to put right.
"The numbers that we are aware of are quite small but I would say that there is a larger problem there," Ms Cox said.
"For the majority of people, they are told by a government department that they are not eligible or something's changed and they just accept it or give up in frustration."
RNZ has asked Medicare in Australia for comment and is yet to receive a response.