From my personal experience and also from studying various religions and occult teachings, I believe that the highest level of Ascension we can achieve here on Earth is that of Oneness.
Are there higher levels of Ascension the Oneness?
There are definitely higher levels of Ascension than Oneness.
Personally, I can only help you to the level of Oneness. After that you will need to find another guide or track a path yourself.
How do I know there are other levels beyond Oneness?
1. When in Oneness, although complete and whole, I am aware of areas of existence that are beyond my comprehension as a human being. This would suggest that the Oneness we experience is not complete, but it is not like that at all. Oneness is all of existence in this universe. However, our universe is like a cell in a body. It is complete in itself, has all the information for the entire body, but it is not the body. There are other universes the nature of which we cannot imagine because it would be like a rock at the bottom of the sea imagining existing like a bird in the sky. The realities are so different.
2. Logic dictates that even our highest experiences of Ascension here on Earth are limited by the nature of creature that we are both on Earth and in all the dimensions of the Universe we inhabit. Therefore, it stands to reason that there are realities and levels of awareness we cannot reach from life on Earth.
I have not personally met anyone on Earth who has experienced Enlightenment or Ascension beyond Oneness. And most get stuck on Non-Duality, plus a whole bunch in just Enlightenment (in their light/God nature).