In my experience, cabin temp is controlled from the flight deck not by the cabin crew.
Must depend what you fly, I've experienced both methods....
On the 747 classic the individual zone temps were indeed controlled from the FEs station on the Flight Deck..
On the two more recent Boeing widebodies I've flown (744/777) whilst there's a master temp controller on the flight deck which sets a reference or mean temperature for the whole system the individual zones are controlled around that reference temperature (within a certain tolerance ) by the cabin crew, either from the Senior Cabin Crew Members station, and/or from individual zone temperature controllers at certain doors.
In normal Ops we set the Flight Deck master controller to a suitable position during the pre-flight and almost certainly ( as in over 90% of sectors) won't have to touch it again during the sector, leaving the Cabin Crew to control their own zones. If there are real problems getting a particular zone cooled we might lower the system "mean" temp on the Flight Deck master control, and in extremis if the individual zone controls fail we're then back to trying to run the system from the flight deck controls, but most of the time the zone temps are controlled by the cabin crew.
Hope that helps.