confusing PIP decision letter

Hi I have just received a confusing PIP decision letter from the DWP awarding me 11 points for daily living component and thus placing me in the standard rate group from the 4th November 2015 until 28th September 2019. They have also come to a decision that I am not entitled to either rate of the mobility component from and including 8 July 2015.
My pip assessment was carried out on 29th September 2015 and prior to this I was in receipt of DLA. How can they retrospectively rule that I am not entitled to a benefit that I was not even in receipt of.
Secondly, and more seriously, they have said that I am not entitled to either rate of the mobility component.
On page 4 of 8 of my decision letter it clearly states in bold letters that my total score for mobility activities is 12. this is because I cant move more than 20 metres.
In the decision makers own words, as to how he has reached his decision, 'The evidence indicates your medical conditions cause you substantial difficulties with moving around. this is consistent with your medical history, your description of a typical day, informal observations at your consultation, how you engaged with your assessor and the available evidence.
How do I deal with this Orwellian bullshit?
I phoned them, earlier today, and they said they will be back in touch within 5 days, as there has obviously been a mistake.
Should I believe them and hope that they will come to a rapid and quite obvious decision in my favour, or should I be more cynical and put a mandatory reconsideration letter in immediately.
I haven't got a clue where they have plucked the date 8th of July from, so if anyone has any insight that they can offer me will be much appreciated.
I think my decision maker needs a wca assessment himself as he seems incapable of understanding a simple sentence. THIS MEANS YOUR TOTAL SCORE FOR MOBILITY ACTIVITIES IS 12 POINTS. Seriously any help, as to how I deal with these idiots, will be most welcome

love ray

Hi Gordon!
Just to let you know that I had a call back from the DWP and they acknowledged the contradiction of awarding me 12 points for mobility but stating that I was not eligible for either higher or lower rate mobility benefit.
The woman who was dealing with my claim was very apologetic and agreed that I was indeed entitled to higher rate mobility benefit and claimed the error was completely her fault because she pressed the wrong button on the computer.
Something that struck me, in my initial telephone conversation with this decision maker, was that she asked me if I intended to appeal this decision, to which I replied "of course! I will take this to an upper tribunal and beyond if necessary".
She replied "No I don't mean the mobility decision, I mean the lower rate care award decision".
I replied " I don't know yet, I'll have to discuss it with welfare rights first"
I wonder if her decision would have been different if I had said that I was, categorically, going to appeal against the care component decision too. I feel I would have grounds to do so as my mobility award was based on the grounds that for the majority of the time I am bed bound, i.e. can't walk, can't self care.
Anyway I 'm gonna leave it as it is.
I'm over the moon with the decision of higher rate mobility and lower rate care, thanks for all your help.
Your guides to filling in pip forms are excellent and made the whole process of claiming PIP a lot less stressful than I could possibly imagine
My award is until 2019 so I feel I can, hopefully, relax for a few years.
keep up the good work

Let the good times roll!

Ray Charles XXX