If Price Empty

please help,
if price empty, can change display price with call for price?

i use this on function.php but didnot work on Carousel all in one
/**
* This code should be added to functions.php of your theme
**/
add_filter(‘woocommerce_empty_price_html’, ‘custom_call_for_price’);

function custom_call_for_price() {
return ‘Call for price’;
}

thank you for yr support

https://wordpress.org/plugins/woocommerce-products-carousel-all-in-one/