Write a letter to the manager of a restaurant

Dear Manager,
I visited the Nandos on March 12th with my friends for a birthday dinner. I was very excited on that day because it was a special day for me. I am your loyal customer and I have been visiting for the past 7 years.
Even though, I arrived 15 minutes before the reservation time which was 08:00pm, I still waited more than an hour. Eventually, we were taken to our table after a long time, but my worry just didn’t end there. The waitress served us wrong food and upon inquiry she wasn’t responsive either. Being a customer, I was very infuriated with their behavior. The special moment which I arranged on that particular day for my friends was utterly ruined simply because of your impolite staff.
In the past, I never faced such problem. I used to enjoy my visit every time I visit your restaurant. But I’m sorry to say if this attitude towards customer doesn’t change, then your restaurant will lose customers quickly. Therefore, I advise you to improve customer satisfaction and staff hospitability.
Sincerely,
XYZ