Copy the following code on your Child theme’s functions.php.

add_action( 'init', 'custom_block_users_backend' );
function custom_block_users_backend() { 
	global $wp_roles;
	if( $wp_roles ){
		$wp_roles = new WP_Roles();
		$wp_roles->roles['wpcargo_client']['name'] = 'Custom Client Name';
		$wp_roles->role_names['wpcargo_client'] = 'Custom Client Name';
		$wp_roles->roles['wpcargo_driver']['name'] = 'Custom Driver Name';
		$wp_roles->role_names['wpcargo_driver'] = 'Custom Driver Name';
		$wp_roles->roles['wpcargo_employee']['name'] = 'Custom Employee Name';
		$wp_roles->role_names['wpcargo_employee'] = 'Custom Employee Name';
		$wp_roles->roles['cargo_agent']['name'] = 'Custom Agent Name';
		$wp_roles->role_names['cargo_agent'] = 'Custom Agent Name';
	}
}