hey bro ,,,never fight with those stupid amigos....coz they are  crazies.....and dont fight and argue much with those niggers too....these are the worst human beings on the planet....i dont know how long you been working n a gas station but i had worked almost more than a year....and these people have nothing to lose..we have a family back home to take care of..we cant be hippies like them.............best solution is to say that you are going to call the police if you see them stealing or argueing with you for no reason,,,,unless it gets out of control you dont have to call the cops....just pretend like you are dialing some numbers and calling a cop...just show him that you are calling a cop...say on the phone that you need a protection because a costomer is messing around and getting out of control........believe me they fear cops....good luck dude