Had a similar experience: this awesome takeaway / pizza place had an ordering system completely online, great!

The only downside? After deciding what to eat, adding the table number and pressing "order"... you discover that you can only pay by credit card (I mostly use debit).

No option to pay in cash. I had to go to the cashier, re-order everything, tell her my table number and pay in cash.

Not that huge of a deal, first world problems, but still - they could have stated right away the payment methods for the online thing.