John Dory's bad service

We visited John Dory's in Mimosa Mall for the 1/2 price. When we sat down they informed us that we may not take from the belt, we need to order from the kitchen. We placed our order. The waitress came back and said that the half of what we ordered is not available and we will wait for approximately 45 minutes. We called the manager and informed her that this was not appropriate as they advertise 1/2 price. She could not answer, but informed us that it was a busy day. This is not acceptable. This is not the first time we received bad service.