I didn't say you are unreasonable - I said from what you posted, you sound unreasonable - but it sounds like there is more going on. You implied that in your first post. However, no one here is a mind reader, and you'be given us very little to go on.
Do they know that you have health issues, so communication by letter is preferable? They don't need to know the details, just to know there is a reason why you don't talk directly.
Why do you think they're trying to piss you off on purpose? Going by the little you have told us, it sounds like they did accidental damage which they have tried to put right, not deliberately picking a fight. You may be right about them, but we don't know any more than you've told us to be able to judge.
You are being unreasonable to say anyone an do what they want - that is not the case, and you know it, and in saying it, you sound like a stroppy teenager - again, I'm sure you're not, but it's how your writing is coming over - and if you can only communicate by writing, then that's going to be important.
Other than the letter from the hospital, how are you managing stress? Do you get any counselling or anything, to help you build strategies to handle difficult situations in ways which are less likely to cause things to escalate? Maybe you need someone who can help you write things in a way that is assertive but not confrontational, so you can get your point across in a way that doesn't get other people's backs up. That way, the outcome should be more successful and less stressful for you.