The staff member who created this page on behalf of Aventus is no longer in their employ.
You can try following the directions at
Recovering hacked/lost accounts, but it sounds like you made mistakes with your employees.
We either need permission to delete the page or to to update the page.
I highly doubt that's going to happen if you can't prove ownership of the account. Bitcointalk is all about freedom, not about censorship. And I've
never seen someone get edit privileges in someone else's topic.