dear sir, i have a multipule visa for 180 days for china but each stay is not more than 30 days... the problem is this i am coming to shanghaifor work in expo 2010 and the expo is for 180 days...so i just want to change my each stay 30 days to 180 days pls confirm is it possible now i am in shanghai so pls cofirm where should i contact to extend my stay.