Would like to actually order a sandwich???

Just attempted to use the app - when I go to checkout, first it requires that I attach a card (I originally wanted to pay cash in the store?) (also it would be nice if this could be made clearer as a REQUIREMENT, I went around in circles with the dialog box for a few seconds looking for an alternative), and then it advises me to wait for the cashier to finish, and resubmit. What cashier? I got this error a few times before I finally gave up.

I hope for your sake that my card hasnt been charged, this was a massive fail. It would have saved time... If it had worked.

Argent Ocelot about Subway®