Share certificate

I have purchased a flat and even started staying there since an year. I am paying all monthly dues to society and even i have submitted all registration document to society . To get the Share certificate moved to my name i have to get signature from seller but he is not co operating , is there any way to solve this problem. I have all legal purchase document but re seller is not signing the required forms. please assist to get the share certificate. Can society send the letter to re seller for no objection?