nikah se pehlay mujh se blank stamp paper per sign

Father in law nay nikah se pehlay mujh se blank stamp paper per sign lay kar stamp paper may apni marzi ki sharaet likhi hay ab wo na os stamp paper ko theek kar raha hay na original stamp paper hamay dikha raha hay aik photocopy stamp paper ki os nay di hay ab hum kiya kary es stamp paper ko kaisay cancell kary kiya bawaqt e nikah nikah nama may es stamp paper k bary may kuck likha jae ya koe aur tareeqa hay jis se ye stamp paper effective na rahay ta ka future may ye stamp paper hamary khilaf ghalat estamal na ho sakay jo sharaeth stamp paper may likhi jati hay wo wali sharaet valid hoti hay ya nikah nama may jo likhi jati hay wo wali shadi abhi nahi hoe honay wali hay please guide kary