JDE SOAP request - <contactId> is returned 0 - getContact

Hello,

I am trying to update phone number and email id of who's who related to an address book number.
My question is ,

"Is it possible to update an existing phone number and email id. Or Do we need to delete the existing one and Add a new one."

I noticed an element named <contactId> under the Contact name space .

WSDL i used is : AddressBookManager Service

Method i used is: processContact.

Also When I tried to query for an address book's who's who record the <contactId> returned was 0. With this, I am unable to update any existing phone number and email id.