Monarch staff have revealed that they were forced to call a premium rate number to hear their redundancy news, with some forking out up to £40 for the privilege.
The British Airline Pilots' Association (Balpa) discovered that employees were asked to join a conference call if they could not make it to meetings discussing lay-offs.
The call - to an 0844 number - lasted for more than an hour, with many racking up sky-high bills in the process.
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Monarch staff have revealed that they were forced to call a premium rate number to hear their redundancy news, with some forking out up to £40 as a result
Balpa has described the treatment of Monarch staff as 'shabby' and 'cold-hearted'.
The group's general secretary, Brian Strutton, said: 'I am shocked to learn that this was a premium rate call and that pilots and other staff have been charged £40 for the privilege of being told they are out of a job. A kick in the teeth when they are already down.
'This is unbelievably cold-hearted.
'Since Monday we've seen appalling treatment of Monarch staff. Not only were they given no warning of this situation but some have had to shell out their own cash to be told they've lost their job.'
He added that the way the pilots were notified of their company's demise and their own sacking was 'shabby'.
A spokesperson for KPMG told MailOnline Travel that the joint administrators are seeking to rectify the situation.
They explained: 'Having asked a third-party provider to set up a conference call for Monarch employees on the afternoon of our appointment, and agreeing to pay for that call facility, we have since been made aware that each of the participants was charged an additional sum by their phone company to join the call.
'We will ensure all participants are refunded any additional costs they incurred.'
The British Airline Pilots' Association (Balpa) discovered that Monarch employees were asked to join a conference call if they could not make it to meetings discussing lay-offs
In response, Strutton said: 'This is a small mercy in troubled times and we're glad that common sense has prevailed.'
Monarch's collapse - the largest to ever hit a UK airline - happened at 3am on October 2 when all planes were on the ground and could be seized.
It caused chaos as travellers arrived at airports across Britain and Europe were told by text message that their flights were cancelled. No staff were on hand to speak to distressed customers.
More than 2,100 Monarch workers also lost their jobs but were not told in advance of the announcement, leaving many in tears at its Luton headquarters.
The Civil Aviation Authority admitted it knew the airline was in trouble early last month.
Since Monday, Balpa has lined up potential job opportunities with 22 different airlines and has arranged a 'Flight Crew Futures' event to take place on October 17 at Gatwick.
Strutton added: Our National Executive Council has issued a message of support to Monarch members and we have assured them that we will work tirelessly to get as many pilots as possible into new jobs as soon as we can, so that their skills aren't left to go to waste.'