Unhappy client

I visited the Musgrave centre branch this evening, leaving very upset and unhappy, firstly I gave the waitress my order at about 17:15 and told her I had a birthday voucher, she said she will come back for my card, but I waited and waited and waited she didn't come back, then I was so fed up, cause my son was hungry cause I came straight after work, I went and spoke to the male manager on duty and that time it was 17:45, the meal was prepared, but she didn't bring it to us, I then asked for the bill and I gave her my card, she then came back saying that my voucher was expired, I was furious at this stage, cause I came abt 2 weeks earlier when I was passing by the restaurant and asked one of the waitors who was a male not sure of his name, he took my card and said he's going to check the validity of the voucher, he came and said not to worry it will expire at the end of September, so that's why I came through tonight, the female Manager on duty, came to me with a statement and told me that the voucher was expired, she didn't listen to me at all., just told me it was expired, I am so dissatisfied with the service and the way I was treated, but most of all, I'm not sure you can rectify thile situation,

Thanks