Just got pip standard

Hi again just letting you know that a had f to f assessment about six weeks ago they dropped me from enhanced pip down to standard pip and nothing for mobility so I will ask for a MR the date on the letter was a week ago so now I have only 3 weeks for get a MR so could please tell me how to go on do I just ring and ask for MR or do I have to write to them the I told the assessor that my sister makes my 3 meals a day she said that I have no problems making meals the reason I can’t make meals I keep falling and no grip in my left hand with my knee injury, where I nearly lost the use bottom half my leg so I can drop to the floor sometimes or my knee can lock on me I dropped a pan with cold water with potatoes thank goodness it was cold water so I have scans showing how bad my knees are also I had my legs crushed which now I have had painful, vigourous veins also my legs are swollen with water tension I also have sciatica down my left leg due to falling down stairs and bulging C7 disc in my neck which affects my left arm and a lot more so please give me any advice on to go on a do have a support worker as well but I think she is on holiday thanks