Nobody can help you here and venting about Nexon is more likely to do harm than good when it's done like this.
Ask to elevate the issue to a higher up.
These people are here to help you, try to remember there's a human behind that chat log who has limited access to what they can and can't do.
Open another ticket up and be on your best behavior. Don't lose your cool because you aren't satisfied with the ways things are going.
It's frustrating sure, but sucking it up and dealing with an annoying process is better than losing your entire account.
Edit: It should also be noted that the Migration was 2 years ago, not 4 and that if you were part of EMS and didn't opt-into the merge, your account was deleted.