So I got permabanned because of a hacker

This is weird, I had stopped playing league back in march and only came back for a day reupdate and play a game or two to see if I liked it. I didn't and left again, I came back again months later to find out I was permabanned. I don't know why since I have never been in trouble before and looked at the logs. I see this. Game 1 In-Game senki667: dont come to my lane unless I ask you to senki667: sb senki667: this is why u belong in silver senki667: retarded animal i get queued with senki667: he cheesed with ignite hes not good in the slightest u fucking monkeuy senki667: i dont even want this useless kayn to win for opening his mouth i have over 20 accounts senki667: and i think none of u deserve to win this game senki667: chat restrict or ban this riot idgaf senki667: on a vpn anyway u wont get my other accs senki667: autistic %%%%%% kayn with swiftness lmfao senki667: enjoy this loss

Problem here is that I had never said it and it was only looking at the comments that i noticed someone had hacked me. I have never been banned or suspended/muted before, the most I ever got was a leaverbuster once because I got disconnected from the wifi. Even the match history shows someone somehow got on my account,played 4 games with champions i would never take to a match. Just to get me banned, I never even received any notification by email which made me take months to notice. I honestly want to know how that was possible and why would someone play just to ban my account. Currently opened a live chat, anyone know what I can do about my security and to fix this?