terminated for taking a lunch break

i worked for usps as a temp. letter carrier. On 8/18/2009, i was carrying a 6hr route. i took an 1/2hour lunch break. It was a hot and humid day. my start time at 10am and end time at 4:30pm. The next morning, the supervisor approached me and ask me ,"how come you were late back to the station?" i told her, "i took a lunch break." she said, "you don't get an 1/2hr lunch break." my response was," i don't get paid for the 1/2hr lunch break and you guys automatically deduct 1/2hr of my pay." USPS deducts 1/2hr for working 6hrs. She said, "i will talk to the manager about this." on 8/20/2009, she left a message on my voicemail stating," you don't need to report to work today and i need to make an appointment to see the manager." On 8/21/2009, i spoke with the secretary to speak with the manager. she said,"the manager is not in today." I left a message with her. On 8/22/2009, she call me back and told me to meet with the manager on 8/24/2009 at 10am. On 8/24/2009, i met with the manager. He stated that I'm not allow to take lunch for 1/2hr for doing 6hr worth of work. i was let go because of that reason. i am also missing a day of pay. i spoke to the supervisor about this since May 2009. He said he will correct this. please assist. thanks