What do I do? Any advice please after ESA review

I recently had a face to face assessment for esa. It was a review as I was already receiving esa and in the support group. 
I got the decision back I still got awarded esa but placed in the wrag group . I sent back the form with a letter asking  for a mandatory reconsideration 
The decision was to keep me in the wrag group. 
The letter included comments made by the assessor who was a nurse , and basically he lied so much I don’t know what to do next . I feel it could have been these lies that possibly decided which group I was to be placed in . I wish I’d had this information before I sent off the M.R. 
The letter was quite rude too really. There was so much information regarding my condition which is depression/anxiety/ personality disorder.But the decision maker said they ‘prefer the evidence given by the assessor ‘ . But half of it was lies . He kept asking me how I was after having operations in the past that I never had .He said I use all household appliances. That wasn’t even spoken about . The main thing that was a joke was that he read from the computer that I had depression/ anxiety/p.d and read out medications I was on along with other information that was all supplied from the g.p. and not just what I put on the form . 
In the letter the assessor made up that I told him all that but I had no evidence to back it up. 
What do I do? Any advice please. Do I go to the Dr’s or CAB . The next step is the Tribunal but I’ve read that can be really scary .