disable the billing fields at woocommerce checkout. sadly it doesnt add to your custom attributes, it just replaces them with disabled.

functions.php

function custom_disable_woocommerce_billing_checkout_fields( $fields ) {

	foreach ($fields['billing'] as $key => $billing_field){
		$fields['billing'][$key]['custom_attributes'] =  array('disabled' => 'disabled') ;
	}
    return $fields;
}
add_filter( 'woocommerce_checkout_fields' , 'custom_disable_woocommerce_billing_checkout_fields' );