"Left waiting for hours after 999 Emergency Patient"

I phoned 999 as I could not walk from my pain in my back. I arrived at Solihull Hospital and the ambulance crew dropped me to the A&E reception. After that I was not seen by any nurse for 3 hours. No one came to see or talk to me even I was on the front of there eyes for 3.5 hours. After I decided to leave, the nurse was running after me to sign a paper, where it says that I was ok to leave the hospital. After I signed the paper and was trying to walk away, she said that I could have told them I was waiting. I was surprised, as they surely should already know that I was waiting. I am worried that the nurse was writing on top of the form that I already signed. I would love to know where I can report this.