You're probably already doing this, but where possible do make sure you get communications between you and MST guy, in writing. So when he says he refuses to make any more appointments, you have this in writing. If he refuses to communicate back to you in writing, then handle it this way - take notes of any conversation with him and IMMEDIATELY follow him with a letter/email in which you state, "In our conversation in person/over the phone on such-and-such date, you stated [xxxxx]. I asked you [ggggg] and you responded with [jjjjj]. I trust I have this as a correct and accurate record; if I am in error, please correct me in writing within 10 days, to ensure my records are as accurate and complete as possible. If I do not hear from you in writing, I will take this to mean that this current record is already sufficiently accurate and complete."
Putting it in this way is not only polite (when you need to be seen to be polite) but it is also making it clear that non-answer will not get them out of committing to a written statement.
Our local Dept of Ed district office uses the technique of replying to a letter, with a phone call. Nothing ever committed to writing, even when I had requested a written reply. So I would minute the conversation and follow it up with one of my letters, to make sure I had them pinned down.
That also meant I had to get darn good at taking accurate minutes, anywhere at all. I remember one call I got from them (a vitally important call, too) when I was walking past a shoe store while Christmas shopping, and had to pop inside to sit down, rummage in my bag and fins something to write on. I ended up taking notes on the back of an advertising brochure, writing with lipstick! As soon as I could I returned to the car for more detailed (less smudgy!) notes. I'd written down enough information to be able to get down a lot more accurate detail, before I forgot too much. And of course, my letter which followed meant that she confirmed what I had recorded, through her failure to reply.
Oh yes, and send the letter registered mail, or hand-deliver it. Registered is best because there can be no argument that the letter was received. If you hand deliver it, it can still come down to your word against his.
Such are the hoops we have to jump through when we become Warrior Parents...
Marg