Username change caused me to get perma ban :(

Hey, so I haven't actually played the game in a while and I was told recently by a friend that I should change my username because Riot is doing some stuff with usernames, so I did change it, however when I logged back in a message popped up saying that I was permanently banned for toxic behaviour, then a window showed up and the logs definitely seemed to look very racist and toxic, however they were not my logs, I wonder if the username change somehow changed my account with someone else's? What can I do now?
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