"Worst service I've ever experienced"

Today (25th April 2017) I arranged to meet a doctor to get a diagnosis for ADHD treatment. I had called up by telephone yesterday and was told I could not book an appointment, apparently I had to call up on the day. However, when I called on the day, this was not true, and I was told bookings on the day were only emergency bookings and I was told the incorrect information. Fortunately, they arranged a slot for me on the day for 4.15 due to the fact I was misled.

I just came back from my appointment feeling slightly disgruntled for a number of reasons. Firstly, as always, I experienced a very long wait (30 minutes) before seeing a nurse practitioner who seemed to know absolutely nothing about my problem and was reading questions off a computer. Furthermore, as I was explaining the issues i am experiencing, I was persistently interrupted by the nurse practitioner because they were "running on a tight schedule". This made me slightly upset as I was trying to describe my problems to them, only being told to slyly shut up. As well as this, the nurse practitioner provided no help whatsoever, and seemed to ask questions only about my childhood, not currently (I am 18). Thus, I tried to keep it relevant by talking about the issues I am currently facing. Additionally, the nurse also said they couldn't go any further as they needed some information from my parents (which I agreed) and the the nurse practitioner stated they were going to write a letter for me to give to my parents. However, nearer the end of the session, as I was waiting for this 'letter', I was never given one and as I asked for the letter, the the nurse practitioner simply said no, they are not giving me one. I was given no instructions on what steps I should take next, and therefore I am still confused about what I should do. The whole session was approximately 10 minutes long, before secretly being told they had no time. I left disappointed and more depressed than I first came.