Just override the below code from functions.php of child theme

/*
CHANGE SLUGS OF CUSTOM POST TYPES
*/
if(!function_exists('service_slug')){
    function service_slug( $args, $post_type ) {

        /*service post type slug*/
        if ( 'service' === $post_type ) {
            $args['rewrite']['slug'] = 'our-services'; // Change our-service with your own slug
        }

        return $args;
    }
    //add_filter( 'register_post_type_args', 'service_slug', 10, 2 );
}