HDFC Bank — Wrong in surname of nominee's name in my policy of hdf life

Address: Kolkata, West Bengal, 91

Dear sir,
i have purchased a policy of hdfc life policy no is[protected] on 29th feb 2016 in which i have mentioned my wife as a nominee whose name is "sarmistha basu" .But unfortunately when i received the policy document i found that there is major mistake in the nominee's surname. In your policy document it is written there nominee's name is "sarmistha das", which should be "sarmistha basu" which i have clearly mentioned in my form.So i am requesting you please help me how i can change the nominee' surname in my policy document