Child custody

I am legal guardian of my son his father, my wife died because of tb, and physical custody is with grandparents, his3 years old now, and this years i have only seen him thrice, they dont have any male issue, and now no intention of giving my son back, at last i had filed case for permanent custody under guardian and wars act section 7, when court summons was issued they said that name and address is not correct its wrong, after that i gave an affidavit that name and address is correct, but again came the same report that name and address is not correct, if same report was to come then what was the use of affidavit which i gave, secondly now i have come to know that they are intentionally avoiding the summons and taking their time, they are looking to sell their flat and to run away with my child, now what legal step should i take to stop them after knowing their malafide and evil intentions, pls guide me.