I was terminated for insubordination, what can i do

HR Director claims some complaints were given about me from the Manager and a On Site Coordinator, he said i wrote an email and they are using the email against me, i wrote that it was unfair to have me work 10 to 12 hours shift trying to figure out payroll for 2 and 3rd shift, i was going home my hours are 9-5pm it was 7pm i was tired. oh and joking with the manager i would tell him please fire me... i really thought we had a good relationship, he would say and make easy for you we are in this together. all along he was complaing about me, i had no idea. all i wanted was to work normal hours. once i began to complaint about the long hours, i get terminated