our order was burned

Our order was burned and complain and we were told that we have to pay as we already eat half of the burger and we won't get anything. All we wanted was the replai*****t of the burger. We. At first the manager came and told us we eat half so we won't get the same burger but they will replaced it with cheaper burger and we will pay for it. I dint understand but that never happenedone we waited later the waiter told us that she was told we won't get anything. I ask her to call the manager. But than later she came we an order of a cheaper burger. We divided to male it a taker way as i was angry.