Can i postpone the joining date in TCS ilp (ignite) and how..?

hey friends ......please help me....i got my joining latter yesterday from TCS...n joining date is 1st july 2011 .....BUT my last semester exams of bca are held on last week of july 2011......so how can i join the ILP ........please suggest me......is there any procedure for getting REJOINING date.....OR there is no hope...?????