Hi 5654847a,
I'm very sorry, but there isn't much help we can give with bans here on the forums. Bans and suspensions are entirely controlled by EA's Terms of Service team, and as such they have final say.
Unfortunately, if they have stated that they believe the ban to have been placed correctly after multiple investigations, then the account will remain banned, I'm afraid. You can keep trying with the appeal process (here: Get information about EA Account locks, bans, and suspensions), of course, but further appeals will potentially be rejected straight away.
However, if you are unsure of the reason for the ban, you should have been provided with a general reason in the notification email, and it may also appear when viewing your ban status in the "My Ban History" section of your EA account.