Hi Mininmotion.
I'm sorry to hear that your PIP has been reduced.
The next stage is to put in for Mandatory Reconsideration. You have one month from the date on the decision letter. If you have a telephone assessment, then you should ring the DWP and request a copy of the assessment report - (PA4). This normally takes 7 - to 10 days to arrive. The report should give you more details about why your award was lowered and make it easier to fight your case.
Have a look at the Guide to PIP Appeals - it will tell you how to do the Mandatory Reconsideration.
benefitsandwork.co.uk/guides-for-claimants/pip BIS