Perma Ban HELP

I cant think I ever get banned in the game permantly but here we are... I play the game for more than 6 years. I have always played on the same account and now I get a mail form riot that my account get banned fore the use off a Third Party Applications. I watched what it was and know that I didnt do anything that make me get an advantage over the enemy or anything else. So I ask how can my account get unbanned?