HR inaccurate meeting transcript

Hi,

I'm currently off work with a sick note and have been for just under 2 months. I've been employed by the business for just under 2 years now. Both my employer and myself are based in England. I've provided sick notes from the GP as one may expect. A few weeks ago I was asked to attend a long term sickness review where a HR rep (Acting as note taker) and my direct line manager.

For context, I have a long standing diagnosed mental health condition from a licensed psychiatrist in the UK, and have received treatment via the NHS. Upon receiving the transcript, there are a number of inaccuracies. I've refused to sign the transcript and offered my amends in writing twice as of today (email). The main inaccuracy , which is my main cause for concern was that I had 'not disclosed both my illness or the fact I was on any medication' to the business. Luckily, I can prove this as inaccurate with my onboarding documents.

HR are now wanting to have a 'quick phone call' to discuss my meeting notes and how we can amend them rather than responding in writing. While I may be overthinking (nature of the illness) something doesn't seem quite right about this.

My questions are:

1. Am I able to refuse phone calls for writing as a preferred communication method? I'd prefer a paper trail at this point.
2. If I continue to find the notes inaccurate will there be any repercussion to note signing?
3. At what point do I get a union rep or legal assistance involved?

Thanks for taking the time to read!