Mess up with reservation

My wife made a booking for Saturday, 9th March, and this was confirmed with the above resturant. We received a call from the resturant today wanting to confirm our booking for tonight?. When wife explained that the confirmed booking is for Saturday, 9 March, they now state that the resturant is fully booked. This utter nonsense. Such bad service. My wife made the booking as it is her birthday on Saturday and this resturant made a mess up with the bookings. Never been to this resturant and will never go there after this incident.