What is the difference between individual souls and Bhagavān?

According to Advaita (non-Duality) Vedānta, Atmān and Brāhman are the same. I used to accept Advaita as a fact, but I don't know for sure. Now, I believe there are individual souls which are separate from Bhagavān. I agree with Madhava about duality (Dvaita Vedānta). I think Adi Shankara, Ramanuja, and Madhava were liberated.