My account was stolen and banned from using third party software

Today I tried to log in into my League of legends account after months of not playing the game until I realized that my password wasn't working I tried several times with different passwords I have used in the past but it wouldn't work, so I decided to change my password. Upon changing my password and upon logging into my account it showed me a message saying that my account was banned due to third party software use. Do you think the devs will be able to help me with this issue? I understand that the devs take these matters seriously but I didn't hack my account and would never do it. I really need help.