Changing user role worpress pmpro

I am trying to change user role in worpress, but somehow it does not work. Any ideas?

function my_user_role_change (){
    $current_user = wp_get_current_user();
        //$current_user_roles = $current_user->roles;
        //$current_user_role = array_shift($current_user_roles);
        // Remove role
    $current_user->remove_role( 'subscriber' );
    // Add role
    $current_user->add_role( 'customer' );
    $wp_user_object = new WP_User($current_user->ID);
    $wp_user_object->set_role('customer');  
}

add_action( 'pmpro_after_change_membership_level', 'my_user_role_change', 10, 2 );  
add_action( 'pmpro_after_checkout', 'my_user_role_change', 10, 2 );