Newbie reached desperation point

Saw pain specialist last week. Today, I received a letter from the pain clinic informing me that they have booked me in for three appointments. Each will last one hour and I won't be able to drive afterwards. The letter says I am to have a 'procedure' but there is no indication of what this 'procedure' might be!
I'm a bit (extremely) worried about this. If they tell me what the procedure is on the day, I won't have any time to think about it or research it before agreeing to have it done. If I refuse to have it done, they will probably accuse me of refusing treatment, wasting their time, not wanting to get better etc. That's what they said before when I refused to take medication which would have turned me into a zombie!
Very fed up, miserable, annoyed, peed off.........................