why did i get ban? lift if mistaked

i sign in to my account called oreo dubz god to find that my console and account was banned for a week and i honestly have no clue why. i never got an explanation and even if i did i literally do not know what it would be i made an account for me and my brother to play halo 3 it is a fairly fun game we enjoy it a lot its the only game we own although kids are vulgar and -Yoink!- us and say we suck we do not care, we believe kids take the game to seriously as we just play it for fun win or loss at least we had a good time trying to win.so i sign in to find im banned and like i said i am just baffled and would love an explanation i pay good money to play xbl i have played xbox for five years and never have had a problems with banns of anysort so i am lost… if this is a mistake i would like the bann lifted please get back to me as soon as you can as i would love to get back to playing my xbox live i thank you for your time

Contact Xbox Live Support over this and see if your brother or anybody has been trying to mod the console or such.