Can you email HR?
Dear HR,
Could you clarify the reason for my current suspension?
At 8.20am you asked for me to attend a meeting in front of collegues (name them).
I was asked questions and told not to discuss the reason for the meeting with colleagues or have contact with X.
X, y and z colleague approached me and I informed them I couldn't discuss the content of the meeting.
Colleague A approached me and asked me personally what was discussed. I informed her I couldn't discuss it with her and continued with my work.
I understand colleague A then approached you?
I am now suspended for "discussing a matter I was told not to discuss".
This is not the case and if you talk to colleagues X y and z they can confirm this.
I look forward to your response.
I understand your upset and worried but your posts come across as wordy and this can be unhelpful in face to face situations because it can seem like the "doth protest too much". FWIW I think you've been shafted badly (taking what you've said at face value) but need to use the "less is more" approach in dealing with this in how you communicate. Stick to the pure facts.
Best of luck. Sounds very difficult.