My 91 yr old mother is in a nursing home. There has been a problem with the air condition temp. Any suggestions?

i was told that the maintenance guy put a lock on the unit at 75 degrees. The room still gets cold at times. I can move the temp up and down and I can hear the shift but he says it's still locked on 75. My mother's roommate is cold natured also but she is on the other side of the room. My mother is beside the air conditioner. They both have dementia. I really don't want to move my mother into another room.