Cinemark review: i'm complaining about an issue that happened to me when I was working at cinemark

The cinemark that I worked for I always got the job right I always was on task was a fast lerner and I never got introoble or write up but today a new manager that's use to be an employee went to the gm and wrote me for termination and that is because I was siting in the break room charging my phone about to clock back in and I stayed for at least 8 minutes because I had to charge my phone because it was dead and I needed it on so my dad knows when to get me and she came looking for me saying I already clocked in and I was suppose to be on the floor and I said I understood and I apologized and when on to finish my job and later to ight she callled me in to go in the offince and the general manager was there and she told me she was going to terminate me she did not give me a warning or wrote me up she just fired me on the spot and I never did anything wrong I always was a hard worker and earlier that day that same manager saw me sitting in the theatres when I was waiting for the movie to end because I was ushering and I only sat down for 1 min because I injured my whole leg and thigh from playing softball and when I stand up too long I get a very sharp pain and sometimes I walk it off but since i've been working everyday with a 8-10hour shift and I still haven't gotten a day off my leg was getting in pain badly so I only sat down for a minute and she saw me getting up and decided to tell the general manager and wrote me up for termination so I think that's not right and I deeply need to file a complaint because she said I couldnt have a warning and that I have to leave immediately