Symphony 3.0 Password Change security.yml

Question

A friend who has a Symfony tool asks me to change his password. I am a PHP developer but I don't know Symfony...

I found the security.yml file with the password encrypted in bcrypt (12 passes). When I replace the password by another bcrypt password (12 passes) directly in the code, it crashes when I try to connect (wrong credential). When I put back the old password, it works again...

Any idea ?

# http://symfony.com/doc/current/book/security.html#where-do-users-come-from-user-providers
    providers:
        in_memory:
            memory:
                users:
                    nextstep:
                        password: $2a$12$et/Xz8tDrdB3b5[etc...]
                        roles: 'ROLE_ADMIN'
    encoders:
        Symfony\Component\Security\Core\User\User:
            algorithm: bcrypt
            cost: 12```