I got banned for using a third party software

I Haven’t been playing this game very long ( for like a year or 2 ) and i got banned today for using third party software to enhance my play in league of legends,but i don’t use any third party soft ware on my laptop that could help in a game and i would like to get my account unbanned. I’ve abided by the rules of the game and i put a lot of time and effort into my account . so could someone help me out with this. The only thing i can think of that wasn’t on my pc in the past because i downloaded it tuesday is my norton antivirus program.