A woman who says she unknowingly bought fraudulently obtained airline tickets online claims she's being treated like a criminal by Air Canada.

Canada's biggest air carrier is demanding Ann Qian repay over $18,600 for return flights between Toronto, Vancouver and Shanghai — and has banned her from flying its routes until she pays up.

Qian, 25, says like thousands of Canadians, she was simply buying online. And she calls Air Canada's demands "bullying."

"They say I'm a liar, but they just don't want to know the details. They just [want] me to pay the money."

Qian's lawyer and an air passenger rights advocate say Air Canada doesn't have the right to put her on its "no fly" list or demand she pay for tickets she purchased in good faith.

But the airline says buying tickets online from an unverified seller is akin to buying a TV in a bar.

Air Canada says customers are responsible for verifying they are dealing with an accredited travel agent. (Mike Cassese/Reuters)

Air Canada has rejected mediation, and the dispute will be decided through adjudication before the Canadian Transportation Agency.

3 unchallenged flights

Qian came from Shanghai two years ago to train as a pastry chef at a college in Scarborough, Ont.

She turned to WeChat — a Chinese messaging and social media app — to find cheap flights to visit her sister in Vancouver and her parents in China.

She found a seller with the user name "CaptainCooll" who claimed to have access to "Air Canada employee discount" tickets.

Screen captures provided to CBC News show an ad promising a "hot sale" of up to 50 per cent off.

A screen capture of WeChat seller 'CaptainCooll,' who claimed to offer discounted Air Canada tickets. (Martin Diotte, CBC)

Qian says she didn't realize she was buying from a fraudster who was using a stolen credit card to book airline seats on behalf of unsuspecting clients, then pocketing their payments.

She became a repeat customer after flying three times with Air Canada over almost a year and a half without an issue.

Qian says she paid "CaptainCooll" $5,800 for the flights, which included "deals" on business class seats.

'Shocked, stressed' by ban

But in November, when Qian went to Toronto's Pearson airport to catch her fourth flight, she was denied boarding and told she was on Air Canada's "no fly" list.

"I'm so shocked why I'm on that list … so worried," she recalls. "It makes me very stressed."

She was out-of-pocket for that Vancouver return trip — and for a pre-booked fifth flight to Shanghai — another $3,600.

When Qian confronted "CaptainCooll" online and demanded her money back, he blocked her and then disappeared.

Qian says she contacted Toronto police in April in a bid to find the fraudster.

Air Canada demands $18,683.66

Despite Qian's personal losses, Air Canada insists she owes $18,683.66 for the fraudulent flights she took — and that it failed to detect.

Canada's biggest air carrier is demanding Ann Qian repay over $18,600 for return flights between Toronto, Vancouver and Shanghai — and has banned her from flying its routes until she pays up. 0:26

In a Nov. 29 letter, the airline demanded full payment in 45 days.

That was almost double the total of $9,400 Qian had paid the fraudster.

She was unable to pay Air Canada and says she has no idea how much the airline now wants, given the deadline has passed.

'Hazard to property' cited

The November letter also cited Qian for "prohibited conduct" under the airline's tariff rule that covers "any unusual hazard or risk … to property."

Richmond, B.C., lawyer Kailin Che takes her client through the warning letters received from Air Canada. (Martin Diotte, CBC)

Air passenger rights activist Gabor Lukacs says that makes no sense — and banning Qian is beyond the power of a common carrier such as Air Canada.

"If someone was threatening to beat up the pilot or if someone was smoking in the lavatory, those are grounds for refusing to transport a passenger," says Lukacs. "But an airline cannot refuse to transport someone … just because they have a [financial] dispute with a person."

A friend helped Qian hire Richmond, B.C., lawyer Kailin Che.

"It's unjustified. It's unreasonable," says Che. "There's not grounds for their actions … Air Canada shouldn't be going after the innocent consumer."

Che also wonders why Air Canada didn't flag the problem sooner, calling the delay "baffling."

Lukacs agrees.

"It took Air Canada more than a year to detect the fraud. So how could they possibly expect the customer to know right away?" says Lukacs.

Buying a TV in a bar

But the airline refuses to back down.

In an April 8 email, Air Canada's legal representative rejected Qian's request to lift the travel ban, chastising her for purchasing from a seller who claimed he was an accredited travel agent "without a modicum of verification. With due respect, this is akin to buying a television set in a bar."

Contacted by CBC News, an Air Canada spokesperson refused to comment on the case, but suggested customers protect themselves by buying tickets directly from the airline's website, call centre or through an official travel agent.

Qian says Air Canada's demand for repayment makes her feel victimized twice.

"I think and feel as if life is no hope. You just stay home. I don't know how to figure it out. And start crying a lot," she says.

"I do not trust anyone now."