All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
It seems that the person you went to does not use Sharee‘ah-approved Ruqyah (incantation for cures by Quran and Prophetic supplications) for removing magic spells, since he asked for your mother's name. Only sorcerers ask for such things.
You are not a sinner because you thought that this man was a righteous person who uses Sharee‘ah-approved Ruqyah to remove magic spells and you did well by not doing what he asked you to do. You should warn the person who told you about this man and all others who know or go to him. However, you should not blame righteous Shaykhs because it is quite possible that they really do not know a competent person.
We ask Allaah the Almighty to cure your father soon.
And Allaah Knows best.