"Poor ADHD support - aggressive & combative doctor"

My fiance recently went through diagnosis process for ADHD, after almost 30years of struggling unsupported and unmedicated.

He is now finally getting medication which he has been taking for several months. As part of this he has to attend regular clinic appointments which are currently online over video call.

He had a clinic call at 4pm. The doctor acted incredibly aggressively on the call - any time he tried to speak, the doctor wouldn't let him finish and talked over him, if he didn't stop talking they would just talk louder to drown him out. This is not the first time this has happened and it has got increasingly worse with each clinic call he has been required to attend.

As part of his ADHD my fiance suffers badly with anxiety and depression, which he has told the doctor about but they were incredibly dismissive and it seemed to us like they were almost taking delight in goading him verbally and trying to trigger him. Yesterday this doctor told him he should not be calling his GP with his weekly BP readings (as his Consultant told him to do) and that he should be calling this doctor with the readings which they would pass on. This has never been mentioned before and makes no sense as he doesn't have a scheduled call with them each week. My fiance tried to point this out and the doctor talked over him, he stated he would continue to do as advised by his Consultant. 

This seemed to anger the doctor more, who then told him to make a complaint about them so he can be taken off the list. 

His anxiety is now through the roof as he doesn't want to stop treatment or be taken off the list, he no longer wants to have to deal with this person though as things have deteriorated so badly and wants to be transferred to another doctor instead.

We do not know how or who to ask for this to be done, it is impossible to have any kind of actual conversation with the current doctor as they do not listen and continue to be increasingly combative. This doctor made it clear that they were actively encouraging him to raise a formal complaint so that he can be taken off their list, which is absolutely not what he wants to do.

My fiance says there has been no check regarding his current medication, how it is affecting him, no discussion around dosage (he has been on same dose for several months), and when he has tried to highlight impact to his mental health this has been ignored and basically disregarded. It is a horrendous patient experience with no care or support shown or offered, which is appalling especially for someone who is apparently trained to work with patients with ADHD. 

We are at our wit's end, it was a battle for him to go through the diagnosis process in the first place and it just feels like more and more barriers are being put in his way to stop him accessing the help and support he needs to be able to manage his ADHD effectively.