How to change the Name spelling in legal documents

Respected sir/madam my name is Narayan Prasad Sharma from Dist Nagaon Assam. There is a mistake in my fathers name from long time.In fathers official document there is Himlal Sharma in bank document pan card there is Hemlal Sharma .And in my school certificate and official document there is hemlal Sharma . Last year my father expired ,now my mom going to apply next of keen certificate for taking the financial benifit s from fathers office , My confusion is that in next of keen certificate there will Late Hemlal Sharma ,and in fathers official documents there is Himlal Sharma, In that case if fathers office rejects the certificate ,what should we do???