If the Passenger Service Tax that you speak of is truly a Tax, then it is a government impost, which your employer is legally bound to collect. The same goes for just about any airline that I know of, where even free tickets are subject to Airport tax, travel tax etc. Crew positioning ON DUTY in our own aircraft must enter the aircraft in uniform to avoid the various taxes, a quick change on board follows.
If however, the word "Tax" is just an airline pseudonym for Passenger Service Charge, then it's another matter, an industrial one.