since wppizza version 2.11.8.14

if you wanted to disable a gateway conditionally (lets say no cash on delivery for non logged in users) you could add this to your themes functions.php

add_filter( 'wppizza_filter_gateways_available', 'myprefix_filter_wppizza_gateways' );
function myprefix_filter_wppizza_gateways($gateways) {
if(!is_user_logged_in()){
unset($gateways['COD']);//gateway keys are always uppercase
}
return $gateways;
}