There's no need to receive a warning if you did plagiarism, you can say bad/foul words though but you can't plagiarize. Your account has been banned because you broke a rule/s.
Based on the forum rules:
25. Ban evasion (using or creating accounts while one of your accounts is banned) is not allowed.[e]
33. Posting plagiarized content is not allowed.[e]
I am sorry about this, but the punishment that I have been given is not convincing