Australia Post has been flooded with complaints on social media after it raised its stamp price to $1 for slower letter delivery service on Monday.
Australia Post's stamp for regular delivery service has increased from 70Â¢ to $1 and the regular service will take up to two business days longer than the priority service.
To have the letter delivered within one to four business days, customers will have to use the new priority service at a cost of $1.50. 
Customers must use a special priority label which costs 50Â¢ on top of the $1 stamp. Letters without the priority label will be delivered according to the regular timetable even if it has a $1.50 stamp on it.
Communications Union NSW secretary Jim Metcher said the system was an administrative "farce" and would cause confusion among customers.
He said some customers may use stamps worth $1.50 in the mistaken belief they are using the priority service, when they are not because they have not used the special label.
"If you're paying for it you're entitled to faster service and people should be refunded. The consumer watchdog should be climbing all over this," Mr Metcher said.
He said the administrative complexity may cause customers to walk away from the postal system altogether.
"You can't have a system so dysfunctional that you have thousands of people give up on the postal system."
Australia Post will keep the concession stamp price at 60Â¢ and Christmas cards at 65Â¢.
Disgruntled customers have taken to social media to complain about the higher stamp price and slower service.
"A 80Â¢ price hike for the same service. What a disgrace.
"Auspost, please let a smarter company run our postal service. You're un-Australian," Facebook user Michael Buns said.
"I don't understand why, if letters are able to be delivered within four days, why the regular ones will take longer? Why not just send them all the same way? What's the logic? That's a strange system," another user, Sonya Baker, said.
Others have questioned the leadership of Australia Post boss Ahmed Fahour.
"Ahmed Fahour is paid more than enough to provide for hundreds of more staff but no instead he reduces the staff and he is living in the lap of luxury and sending the company broke and ruining the reputation of a once fine company. He and his fellow board members are a disgrace. Sadly, like many corporations now, customer service means nothing," Alexandra Twitchy said in a social media post.
Sandy Beach, who identified herself as a former long-term employee under the leadership of chief executive Graeme John, said Mr Fahour should be sacked.
"Ahmed Fahour is a joke. He has taken the business to an all-time low. In other businesses he would be immediately sacked. I call upon the board of Post to dismiss this man as he is proven to be totally incompetent," she said.
In the 2015 financial year Australia Post reported a loss of $222 million, the first loss in over 30 years, primarily because of the decline in letter volumes.
Even with the $1 stamp and the slower service, Australia Post is not likely to profit from the letter business in 2016 because letter volume is expected to decline further.
The Australian Competition and Consumer Commission gave Australia Post the green light for the $1 stamp proposal in   November.
Australia Post said in a media release the price hike is only the fifth in 23 years and the $1 stamp is one of the lowest in the developed world.
Key points
Regular stamps have risen from 70Â¢ to $1 while the priority service is $1.50.
Customers have taken to social media to complain.