Snippet to change UPS credentials in UPS Access-point Locator Request using WooCommerce UPS Shipping Plugin with Print Label by PluginHive - https://www.pluginhive.com/product/woocommerce-ups-shipping-plugin-with-print-label/

functions.php

/**
 * Snippet to change UPS credentials in UPS Accesspoint Locator Request. Requires UPS plugin version - 3.10.2.
 * Created at : 22 Aug 2018
 * Updated at : 22 Aug 2018
 * PluginHive Plugins : https://www.pluginhive.com/plugins/
 * Gist Link : https://gist.github.com/xadapter/cb7a9a83b11d953077c57e4bcc8fa072
 */
if( ! function_exists('ph_change_ups_accesspoint_credentials') ){
	
	function ph_change_ups_accesspoint_credentials( $xml_request, $ups_settings ) {
		$new_ups_user_id 		= 'ups_user_id';			// Replace ups_user_id with your UPS User Id
		$new_ups_access_key 	= 'ups_access_key';			// Replace ups_access_key with your UPS Access Key
		$new_ups_password 		= 'ups_password';			// Replace ups_password with your UPS Password


		$xml_request = str_replace( array( $ups_settings['access_key'], $ups_settings['user_id'], $ups_settings['password'] ), array( $new_ups_access_key, $new_ups_user_id, $new_ups_password ), $xml_request );
		return $xml_request;
	}
	add_filter( 'ph_ups_access_point_xml_request', 'ph_change_ups_accesspoint_credentials', 10, 2 );
}