The only way to get unbanned is to wait for an unban wave that happens weekly. Unfortunately, this is not an actual unban that will reset all of your character's levels back to where they were previously.
Instead this unban will make all of your characters max rank (without giving them the rest of the upgrades or max rank plate) meaning you can play multiplayer again but theres basically no reason to play the game after all of your characters are max rank. so unfortunately, you're still affected either way (thanks EA)
Oh, in fact, all the characters in my account are still at level 46, and EA still hasn't fixed it. Do you know what's going on?
