you can use SQL REPLACE function
Example
SELECT REPLACE('"<root xmlns="http://tempuri.org/"><value pid="AN_PW_ID_2" name="Name1" phoneno="1234567890" address="sun" /><value pid="AN_PW_ID_2" name="Name2" phoneno="0123456789" address="moon" /></root>"','xmlns="http://tempuri.org/"','');