Yes, just go to your order in your order history and edit your order. Just make sure you do it before we start cooking it (which could be any moment!).

The things you can currently change are:
Delivery type (delivery/carryout)
Location (delivery address or carryout store)
Delivery time (ASAP/Future)
Quantity of items
Payment method
Coupons

Make sure you save your changes when you're done!