How to change fathers name in all documents

ear sir, I humble request to you before I am not add my father's surname in my all certificate . I write my father's name - Md. Hafiz in my all certificate, now I want to add my father's surname Khan example father's Name- Md. Hafiz Khan this is right name of my father. I don't know the process of how can I add the fathers surname in my certificate, sir I request to you please suggest to me.