A paramedic with early-stage breast cancer was "distraught" when British Airways staff described her treatable condition as "terminal" and refused to swap flights that clashed with her surgery.
Rachel Tait, 34, and her partner Matea Deliu booked return flights from London to Australia for November, to visit Ms Tait's family.
But Ms Tait, who has stage one breast cancer, later found her surgery had been scheduled for during the trip, and the couple contacted the airline asking to swap their flights for different dates.
Ms Deliu said she was allowed to swap her flights for a fee, but Ms Tait was reportedly refused a straightforward swap by staff who wrongly called her condition "terminal".
The airline said it could therefore only refund her, meaning she would have to buy new, more expensive flights.
The couple also claim they were discriminated against by customer service staff who repeatedly described Matea as Rachel's "friend" and "husband", despite them explaining they were female partners.
BA have since apologised and has arranged improved, alternative flights.
The couple described their experience as "appalling".
"I understand that honest mistakes can be made, however when more than four members of staff continue to misgender my partner once corrected, this shows there is an institutional issue rather than individual one," wrote Ms Tait, from Walthamstow, in a letter to BA. "I am deeply disappointed.
"Additionally, a British Airways customer service manager telling me, a 34-year-old female with primary curable breast cancer, on multiple occasions that I have a terminal illness, when in fact I have a treatable type of cancer, was extremely distressing and shockingly insensitive.
"The way this situation was handled has cost hours of my partners and my paid time, hundreds of pounds, caused unnecessary stress whilst fighting cancer, and had led me to experience homophobic behaviour from BA staff.
"Fighting cancer is exhausting and spending hours and hours on the phone trying to resolve this issue is unacceptable service and treatment."
She told the Standard: "I am sure I am not the first person battling cancer to travel abroad and I won’t be the last. I do not want anyone else to experience a similar incident."
Ms Deliu, from Dulwich, said Ms Tait was "absolutely distraught" to be told her condition was terminal.
"They said 'oh actually because it says you've got breast cancer, you've got a terminal illness'.
"And she was like 'wait a minute, what are you talking about? I have stage one curable breast cancer, which is absolutely not terminal'.
"But they were not having it - 'you've got a terminal illness, sorry. I can only offer you a refund.'"
New flights were by that time reportedly hundreds of pounds more expensive.
"She was absolutely distraught. When you're going through the battle of chemo sessions, fully fatigued, being told by somebody who is non-medical 'you've got a terminal illness'... It's ludicrous," said Ms Deliu.
She called their experience "horrific", and said: "We feel our experience was psychologically traumatic enough that we would not wish for anyone in our situation to go through this. Especially anyone within the LGBTQIA+."
BA says it has been in contact with the couple to apologise unreservedly for their experience.
It has refunded Matea's flight change fee, and upgraded both their tickets from economy to business class.
A British Airways spokesperson said: "We’ve apologised to our customer and are in contact with them to resolve this matter. We look forward to welcoming them on board."
