That's right - if you don't have a pin loaded to your card, you'll need to have your signature checked manually, but that can't be done at an unmanned petrol station. If you can't have a pin loaded to your card and you expect you'll need to use an unmanned petrol station (most commonly found in remote, smaller towns - particularly in the South Island), you might like to purchase a Prezzy Card or MTA gift card (don't get a voucher). Both of these will allow you to spend NZD as if you're a local. Or, ensure you top up in larger towns/cities and try to avoid doing so late at night (particularly in smaller towns) - this will give you the best chance at having a 'real' person serve you (and check your signature).