A customer paid the rider by card but the order says cash. Can I change how an order was paid?

Yes, from the All tab of the orders board with an owner login. Each order has a payment method select: an online or QR order moves between cash and the card machine, a POS sale paid in one go moves between your ordinary ways of paying with a correction line in its shift while that shift is open, Split: two methods takes the first amount and works out the rest, and an active house account puts the whole order on that account. POS sales show their real way of paying there. Every change is in the day report with who made it; a refunded, cancelled or already split order cannot be changed. The Orders & delivery tab in the docs covers payment changes.