My account got banned becuz of 3rd party program but I didnt use any of script or anything!

My account recently got banned for using 3rd party program. But I didn't use any of them! I hope this is really a mistake cuz I won a lot of rank games recently and I just think I got reported by others. I just came to NA server for several months and my account is my friend's old account which he doesn't use it now. But my computer only has Skype and Curse when I play league. No other things! Why my account gets banned permanently? Really think this is a mistake! Hope someone can help me cuz I spent lot money on this account! Riot, you just took away my account by no reason!