How do I get my Job Back?

I was recently fired from my job and I had been employeed there for 7 years. When I called to get my schedule the girl who does the schedule told me what I was supposed to work which was thursday and tuesday. I went in on thursday clocked in and was getting ready to start working when one of the office ociates told me that I was not supposed to be there. I told him who had told me my schedule and he told me to go talk to one of the managers and see what he wanted me to do. I talked to the manager and he told me to hold on and he would see if he could find something for me to do. He came back and told me that he had nothing for me to do. I said ok and asked if it would be ok for me to sit in the break room since i didn't have a ride and my parents would be back to get me and he said that would be fine. I was mad because I had a school event I could have went to but instead I was stuck at my job with nothing to do. I sat in the break room and did homework until my parents came to pick me up. Just as I was about to leave (after my parents came back to get me) the manager I had talked to asked me if I had clocked in when I got there and I told him that I did but after the whole situation happened I forgot to clock back out. He told me not to worry about just to doent it on our time sheets and he would take it off later on that night. I did that and as I was about to leave the store manager came out of t he security room and wanted to talk to me. He badgered me and asked me why I was in the store when I was not working and I told him what had happened. Obviously he didn't believe me and continued to badger me and was like well why did you even clock in and all this other stuff. The store manager even talked to the other mananger that had helped me out earlier and he told him everything and the store manager thought I had told him to say what he said. The store manager had told me that he was going to suspend me for a week because of the incident. I said if you feel that's what you have to do then ok that's fine. He then said ok then. As I got up to leave he told me that I could not leave until the situation was solved. Was it not solved when he told me that he was going to suspend me for a week? I asked him what else he wanted and he continued to ask me why I was there and then he said I was terminated. He asked if I was ok with that and of course I said I wasn't ok with that but yeah I ended up getting fired. Management then went on to tell the other people in the store what had happened which they had no right to do. I have tried talking to the store manager about it but everytime I call they give me the run around and whenever I go into the store they always tell me I need to leave the store I'm distracting the workers. What do I need to do? I have called Human Resources and they aren't doing anything either