if ( isset( $request['billing'] ) ) {
            foreach ( array_keys( $schema['properties']['billing']['properties'] ) as $field ) {
                if ( isset( $request['billing'][ $field ] ) && is_callable( array( $customer, "set_billing_{$field}" ) ) ) {
                    $customer->{"set_billing_{$field}"}( $request['billing'][ $field ] );
                }