Devastated Bestjet customers have vented on social media claiming they are owed thousands of dollars amid the online booking portal's chaotic collapse.

Key points: Bestjet's administrators have told customers tickets that are "no longer valid" will not be refunded

Bestjet's administrators have told customers tickets that are "no longer valid" will not be refunded An "unauthorised" email sent from a Bestjet address has added to customer confusion

An "unauthorised" email sent from a Bestjet address has added to customer confusion That correspondence included numerous typos and the direct emails of several airline executives

Bestjet and its subsidiaries, Wynyard Travel Pty Ltd and Brooklyn Travel Pty Ltd, went into voluntary administration on December 18.

A Facebook group set up for furious customers to share information has swollen to more than 700 people, and its founder Kate Ryan has flown to Brisbane for a creditors' meeting on Wednesday.

The meeting will be held against a backdrop of confusion, with claims of "unauthorised" emails being sent from Bestjet addresses to customers as administrators threaten legal action in a bid to seize the company's servers.

Stan Mikolajski in November used Bestjet to book return airfares with Emirates from Melbourne to Warsaw.

He was due to fly in May and, despite being sent his tickets, was told by the airline shortly before Christmas his trip had been cancelled and refunded.

However, he has not seen his money.

"We don't know where the money has gone and whose pocket it's in," Mr Mikolajski said.

Mr Mikolajski, an experienced international traveller who was using Bestjet for the first time, said he had lost about $2,600.

"I felt cheated, robbed and angry a company that was supposedly quite reputable had then turned around and done something like this," he said.

Disgruntled customers vented online, with one writing: "Absolutely Abysmal — Bunch of Slimy Thieves!!!"

'Unauthorised' emails spark confusion

The already confusing situation for customers was further muddied when the company's administrator Pilot Partners warned them to ignore "unauthorised" emails from Bestjet.

One email sent on December 23 from a Bestjet address accused another company, CVFR Travel Group, of "acting illegally".

The email claimed Bestjet used CVFR to issue e-tickets on behalf of several airlines including Emirates, Etihad and Virgin Australia.

"CVFR will keep your funds and make you submit a charge back even though your booking is confirmed," the email read.

Pilot Partners' Nigel Markey said he would seek legal action to seize Bestjet's servers to "prevent any further unauthorised communications being sent".

Mr Markey said there was a "clear process" for Bestjet customers to pursue claims.

However, the administrators also warned tickets that were "no longer valid" would not be refunded.

Many Bestjet customers have been left stranded. ( Unsplash: Chris Brignola )

Virgin Australia said it was honouring flights scheduled for December and January booked via Bestjet.

However that position is at odds with the experience of at least one Bestjet customer, who arrived at Brisbane Airport [on Tuesday] and told the ABC they were not allowed to board a Virgin flight to Sydney.

Emirates told the ABC they would also be honouring flights made through Bestjet as long as customers are able to provide a booking reference.

However, several Emirate customers told the ABC their flights had been cancelled anyway and some even had to rebook the same flight for an increased price.

At least two customers said they were told by the airline that their tickets were cancelled by CVFR because they did not receive payment from Bestjet.

As a last resort, Mr Mikolajski said some Bestjet customers had asked their banks for credit card chargebacks — an option not available for people who paid via BPAY or direct deposit.

"Nobody, not even the airline, notified us that this was actually going on," Mr Mikolajski said.

"We had to find this out ourselves."

CVFR were contacted for comment but did not answer specific questions regarding cancelled flights.