Help needed regarding the conduct of ASD assessors

Hi, I have recently undergone an assessment where my answers were not written in my report correctly and my outcome was heavily biased by a previously unknown mental health diagnosis that I am not longer able to access/look into/query because it was done when i was a child.

I have asked the assessors to explicitly explain why even though they agree I have significant traits that can't be attributed to the previous diagnosis, they will not give me the diagnosis. They do not answer my questions but repeat rehearsed answers just saying that it is the previous diagnosis but not why.

I have a master's in psychology so I know enough about the condition to know I definitely have it (my son is on his way to a diagnosis and my husband has worked within the field of helping people with autism for the last 9 years). 

I began in the process of all this to doubt myself until I read other reviews from this consultancy agency that the exact same thing has happened to other clients who have been assessed there also. I am trying to reach out to the reviewers to ask about their experiences and try to raise a complaint about the firm. I don't know where to start this process and any help would be really greatly appreciated. 

They have multiple people saying that this agency has negatively impacted their lives. They have been very unprofessional to me in my opposition. 

Examples of this:

Conducting an age inappropriate assessment

Writing false information on my reports and not including a lot of vital information I gave them

Not answering my questions and evading important questions

When it was clear I wanted answers and a second opinion becoming hostile and using language to try and dissuade me

Trying to dissuade me from giving another informant interview from a family member even though it was offered to me originally

Messages becoming more and more dismissive and rude from them

I feel I, and others, have legitimate grievances with them and I really need help to know where to go from here

I do not want others to have to go through what I went through with them.

Thank you