Someone hijacked my account and cheated on it, and now its banned

First off, let's make sure your account is completely resecured.

Follow the steps in this article to resecure the account: https://help.ea.com/en-gb/help/account/secure-hacked-ea-account/

I also recommend turning on 2FA for extra account security: https://help.ea.com/en/help/account/ea-login-verification-information/

You can also use this site: https://haveibeenpwned.com to check if your email or passwords have been released to the public via a data breach.

If your mail/password got breached, make sure to never use that password again.

Once completely resecured, you can try to open a new ticket, explaining that you've resecured your account properly and also including any other relevant information that could help the situation.

Unless support has specifically mentioned to not submit any further tickets on the matter, you could try opening a new one to spark further investigation.

Though if they decide to uphold the decision then they probably have more than enough reason to believe this is the right action to take.

Whilst I'm aware that these things can happen, in the end account security is still the responsibility of the account owner and I do hope that this experience helps you realize that it's really important to keep your account data safe.

EDIT: Seems like someone has beat me to replying haha.