banned account

dear riot,

last week when i logged in i got a message that my account has been permanently banned for the use of inprohibited third-party software. Might it be that a mistake has been made because i've never used any hacks or anything like that. I have the account since season 3 or something and i've put quite some money and a lot of time in it. Is it possible that someone takes a look if there were an error made or if someone could clarify why exactly i got banned? I would really like to get my account back.

ps, I missed the 10 year anniversary gifts :'(

kind regards