Carpark taken away head office staff

I work for a large asx listed company and we are moving offices soon. A large amount of my colleagues and I have been given carparking at or close to our current location as a part of our negoiations but not in our contracts. These have been put into writing ahead of signing contracts and in some cases included the value or a carpark in the email ahead of confirming a final salary. The business is now saying parking will end and those who have a current car park agreement will be given $3000 after tax (adjusted in our salary) as one lump sum and that’s it…forever.

Obviously this is only about 6months of parking and essentially a pay cut for us all.

What should we collectively do? Obviously the company has asked the legal team if they can do this and had it signed off but it doesn’t seem right to me.