Replace tracking provider

change_tracking_provider.php

<?php
// Add this code to your theme functions.php file or a custom plugin 
function ast_api_create_item_arg_filter( $args ) {
	
	if( $args['tracking_provider'] == 'dhlglobalmail' ){
		$args['tracking_provider'] = 'dhl-express';
	}
	
    return $args;
}
add_filter( 'ast_api_create_item_arg', 'ast_api_create_item_arg_filter', 10, 1 );