Perma-Banned due to hacker using 3rd party apps
So after not playing League since about Season 5 and recently getting a new PC, I decided to re-download LoL so I can try to climb up again...Only to find that my account has been perma-banned due to 3rd party usage during games. I check my history and see that I was hacked and 3 games were played in May of 2019. I have since made changes to the account to make sure whoever did it doesn't come back in, but now I'm at a loss. What do I do get my account back, if it's even possible at this point?