Bad food with a Bad manager

Me and my friend decided to go and have lunch at Mugg&Bean in Canalwalk this afternoon where we ordered our drinks and food. After our food arrived i started to eat my Burger as it looked so yummy but only to be dissapointed by the bun being sogy and the lettuce that is off where i took pictures and called for the manager. when the manager arrived he told me a old storry about the lettuce was placed on the b un and went into a hot oven or heat thing where it turns black as soon as it gets hot. I then told the manager that you can clearly see from the other pieces of lettuce that its off and that they can take my food away. The manager said how sorry he was and we asked for the bill to leave. The bill came and we got charged for the Meal i had a problem with and i questioned the manager. He clearly then said i am wrong in saying the lettuce is off where he is right by saying its not off it looked like that because of the heat. I wont support Mugg&Bean again as this is not the first time this happens with food we order. If the manager dealt with the problem the right way i would not be writiing this review but he didnt and there for i want this to be an eye opener to each person who orders food at places like this and the customes comes last.