"They said I needed to call Expedia, so I called Expedia and they told me to send copies of my bank statement and ring another number. By this time I was starting to go stir crazy.
"I confirmed with both the bank and Expedia that the funds were indeed held by Garuda."
The Australian Federation of Travel Agents CEO Jayson Westbury said there was no doubt it was harder to resolve problems when bookings were made in a "virtual environment".
"If you've booked online and you've done that effectively in a virtual world, then when you need to speak to a human it's more difficult to commence interaction with a human then if you'd booked with a bricks and mortar travel agency," Mr Westbury.
"I've never heard of something like this happening though and there are millions of travel bookings made online everyday."
Ms Cardy eventually managed to get to the bottom of the issue, after News Corp made enquiries to Expedia.com.au and Garuda Indonesia.
A spokeswoman for the airline said the double-billing was Expedia's fault.
"It appears there has been an error when Tegan was booking on Expedia.com, which could have been caused by refreshing or timing out during the payment stage, and more than one transaction has gone through," she said.
"Our Customer Service Supervisor, Shirley has since spoken with Tegan and it seems the Expedia call centre were unhelpful and just advised that we needed to refund the amounts."
An investigation by Expedia.com.au found the problem was a miscommunication between "the authorisation and capture process".
"Normally this is a seamless process but in this rare instance, this process hasn't worked."
Ms Cardy said the experience had tainted her excitement about her upcoming holiday.
"I don't think I'd go through Expedia again, and I certainly wouldn't go to Garuda," said Ms Cardy. "At least now that I have access to my money again, I can finally start looking forward to our trip."
Mr Westbury said travellers who experienced issues with online travel agencies could lodge a complaint with AFTA.
"We do have OTA members, who, in order to be accredited must have an appropriate complaints-handling process," he said.
"But (travellers) first port of call can be us, if they have a complaint."