you can also try visit the ICICI bank branch having govt txn authorization, provide your existing PPF details and ask them to provide the details. Also pl remember that only some ICICI branches are authorised to handle govt txn so PPF or SSY account can only be opened in those branches.
is there any specific reason why you want to change the servicing bank? also this may not be the right time to switch. the transfer takes time, during which the account would remain suspended for txn. so better to wait till end of march, get the interest for the current year and then initiate the transfer.