sure name change in govt job aplication

sir my name is parbati namasudra from karimganj Assam.After marrage I use my husband sure name das .my school certificate name is parbati namasudra and now some of my docoments is parbati das.and some of my documents is o arbati Roy becose before my marrage my father change his surename Roy at the place of Namasudra by a court afidifit.now sir I want to aply RRB guwahati but sir I dont understand which surename I use.plz help me sir.