I am the expert on this....
Ok - if the doc is in his own practice you call and ask for the office manager. If it is the doc's office we used to use, then she will avoid you and you will never get to speak to her. (I ended up switching docs because of the office staff)
If the doc is with the hospital, as in you saw them in the ER, you call the main number and ask to speak to the person who can handle complaints. If it is MEC - I do believe they affliated with a hospital - and just find out who signs their paychecks, and that is the person to talk to.
You can message me privately if you need any thing else!