I was on a flight operating from Freetown(Sierra Leone) and about 3 hours during the flight me and my fellow crew members sat at the back seats of the B757.I was listening to music when the lady(who is african) ask me where the toilets was.I said its just at the begining of this cabin on the side and pointed at the toilets at L3R3.When i looked up again I saw the lady tried to open L3.I flew over my collegue and ran to her and couldnot hold it back and yelled to her:"Are u F%*&crazy"Wich she replied she cant get the toilet door open.I told her that that door was an armed aircraft door and not the toilet door..........I still laugh about it when it cross my mind but on that day it scared the life out of me cause i didnot knew that a door cant be open during flight