add_filter('woocommerce_get_availability_text', 'Computec_change_soldout', 10, 2 );

/**
* Change Sold Out Text to Something Else
*/
function Computec_change_soldout ( $text, $product) {
if ( !$product->is_in_stock() ) {
$text = 'אזל מהמלאי';
}
return $text;
}