Face to face assessment

I'm sorry to have to keep posting but new problems seem to be arising all the time. I went to see my MP today, obviously with everything going on on politics lately he wasn't there. I spoke to his advisor and tbh I felt he was quite negative. Didn't seem to fully understand the concept of lack of insight.although I understand he has attended courses on mental health and vulnerable people. He "may" be able to help. When I told him that Capita and DWP had told me (3 different people) I could postpone the assessment (but only once) and I intended to do this in order that I can, hopefully, get help from my MP and perhaps other sources to change the assessment to s paper one. He then became very dismissive and said "Oh they may tell you that, but it's not in writing is it? When you ask definitely, they will say no, and he will be put down as a no show and his benefit will immediately be stopped" I came away feeling even more stressed and down!!!

I checked the web and it says that an assessment CAN be postponed once. So should I take the chance? Is he right to be so negative?