Need Your honest advice urgently

Hello there. I am in great need of your advice!

I got premium account as gift from the friend 2 years ago so I can skip queue. I geared druid and DK to 6.3k gs and I am actively playing on them.
However TFA is enabled and I never knew email for that account and someone else is using those chars right now, but I can still access them through game (normally).
I have realized my mistake and I want my characters to be deleted, because I would rather have them deleted than someone else using them or risk password being changed and characters out of my reach for good.
BUT
I don't want those chars to be restored by ticket or any other means.

What are the ways of successfully deleting character without any other means to be retrieved?
Can I just delete them and create exact same name characters on another account?
Or do I have to use cheat/bot in order to intentionally ban that account permanently from use to successfully prevent usurper using it ever again?

I know it's bit unusual request , but what would be your advice?
Thank You in forward

We don't offer support when it comes to problems arisen due to the account being compromised by account sharing. Which means, the only way to achieve what you're looking for, is to delete and hope the deletion goes unnoticed long enough for the time limit to restore them to lapse.

Honestly, my suggestion to you, is to just drop the account and move on, and don't be petty about it. I would prefer to encourage you to be kind. Don't be to others that which you would dislike or hate. You'd be better off for it, you wouldn't feel dirty after having done it. It might be worthwhile to reach out and contact whoever else is using the account, if you're able, and perhaps talk to them about it. But, again, I would encourage kindness. Be better, do better. It's worth it, I promise.

If you still know the friend, who gave you the acc.. You could ask him the e-mail, then change it to your e-mail..
Or if you still have the access to acc on website. You could simply change e-mail you're self. Then change password.
If other person that uses acc, he can change e-mail password also.. (So it's best to change both)

My acc once was stolen.. E-mail/password changed.. I e-mailed warmane to simply restore "original" e-mail/password that was used to create the acc.
They did that..
Then i changed them again.. And all was saved.

do the same thing a scammer would do,
delete or disenchant (if enchanter) the gear, send any gold and items to alt account
this will greatly discourage the use of the account.

not sure if you can immediately use the name again if you delete the charactor
but you could try it.