Trying to update the WooCommerce payment method as part of an AJAX call. I'm currently running this line;

function ajax_payUsingVCAccount(){
    update_post_meta( esc_attr( $_POST['order_id'] ), 'payment_method_title', 'commission' );
    die();
}

But the payment title doesn't update the POST variable does contain the correct order_id.

When I dump out the payment title afterwards it's just an empty string.