Account Suspended

Hello, I didn't play much League of Legends lately, because of my full time job and studies. I accessed my account about 2 weeks ago, after a long break, probably June. I noticed my IP has been spent, I had champions I didn't own/bought myself. I checked match history, a couple of matches were played 1 day before I logged in. I proceed to change my password immediately because someone disconnected me from the account while I was logged in. Changed my password and started playing a game or two. Tonight, I try to log in again for a casual match. My account permanently suspended for malicious 3rd Party Software use. I never used/owned/intended to use such software, I own this account for a long time, over 5 years, I really care about this account even if I didn't play much lately. The IP addresses that accessed this account can be checked right? The location can be seen as well. Maybe it can be seen what happened. Anything that can be done about this?
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