My Account has been hacked

I was trying to access my league account and it says my password or username is incorrect. However, I have my password and username saved on the game and website as well. I could not access my in game account and when I go to try to log into my website account I can access it because I bookmarked it with my username and password, but i can not manage account because it asks me to sign in(Which I can't). They have also changed my email so I can not recover my password or username because everything has been changed. I have had my account since season 3. Please send feedback and help ASAP(End of Season).