1.It is free of charge. It's compliments of our restaurant.
2.I'm very sorry for my clumsiness.
3.l'm very sorry to have spoilt your evening.
4.We might have overlooked some points.
5.There could have been some mistake. I do apologize.
6.I assure you that it won't happen again.
7.Please feel free to contact us if you have any requests.
8.If it really bothers you,I'll replace it for you.
9.Would you like to have a new one or change to another dish?
10.Sorry, would you like it cooked a little more?