Lost written MR request letter

I had my MR request handed into my local JobCentre ( as per advice from the DWP call centre - as they suggested this was the quickest means for it to reach them ) for which I received a compliment slip dated & with the receipeints name, my name & NI No.
This was on the 11/1/18
I chased a response on the phone on the 17th, to be told I would hear back one way or the other by the 26th, today. I have phoned today as I have not received anything to now be told DWP do not have my letter on file.

I have since had a call from another dept in DWP again stating they have nothing but asking what my letter said in order for them to make a decision. This person was quite rude ( thankfully I have recorded the whole conversation ) & was goading me. I have said they should base the MR on my written request not snippets of information he was typing during our conversation.

I am submitting a duplicate copy of my MR request on Monday to my JobCentre Again.

I am wondering if it is worth involving my MP ( if he is able to do anything ) since I have been so misinformed by various call centre DWP staff. I ve been addressed frequently by the wrong title & Christian name, they contact me via the wrong phone number although I always update any changes & the general rudeness & distain with the manner in which I was spoken to today.

Can an MP help? Letter of support etc. Does their support carry any weight with appeals etc that you’ve heard of previously.

Thanks