Which userids have you tried? Are you using the system as delivered by IBM? There are several userids supplied that have the ability to change a RACF password. If you don't have any userids you can use, you're going to have to switch to another RACF database. Not an easy process and you'll definitely need experienced sysprog help to pull it off. This is not something that is easily described here.
RDzJohn
RDzJohn