DWP want another PIP assessment as not happy with their first assessors report!

I've got 2 discrepancy on my claim I phoned and apparently what I've put on a couple of questions isn't the same as the assessment I have been truthful on all my questions will wait and see what my report says I'm already on lower living component but now claiming mobility as I've osteoarthritis in my knees and hands waiting on a full knee replacement. My hospital specialist was good enough to have a report typed out for me explaining the situation and listing all my meds as I also have ptsd and schizophrenia I was on full living component 3 years ago but last year was dropped to standard rate which I thought was very unfair as my condition as not and will not improve