being moved from income related esa to contribution esa after transition to UC

Hi i hope i can make my issue understandable, difficult when i do not understand any of it myself. I am appointee for my 42 year old son and have been since he was 5 years old. He went from DLA to ESA and was placed in the support group income related ESA. Like someone else who wrote on your site my son was initially given contribution based and was amongst those who received back pay when the error was recognised and rectified.

End of August, we received a letter asking my son to migrate to UC by 19th November and after speaking with Citizens advice a couple of times was able to complete the migration to UC albeit with a couple of glitches. Or so i thought. We have now received a letter from ESA as other members have reported to say my sons income related ESA will be ending ( which i had understood) and that he would be getting NS ESA as well as UC. The letter said he was in contribution ESA

My son has severe cerebral palsy and can do nothing for himself. He requires help in all aspects of his daily life and has not worked ever nor ever will unless science can undo the brain damage he suffered during birth. Sorry i digress in my frustration! We do employ personal assistants through the local authority direct payments. We use a payroll company to help us make the correct payments to personal assistants as well as paying HMRC taxes and national insurance. I am wondering if this is why he has been placed in contribution based ESA. When i called them the woman i spoke to was unable to answer any of my queries and kept saying we would need to cancel ESA and make a claim for UC. I kept telling her we had just migrated to UC and she simply kept repeating the decision maker had decided and there was nothing i could do about it. I feel frustrated and totally in the dark as to what has happened. Can anyone clarify this mess. It was all meant to be so simple oh yeah sure!! Anyones help so much appreciated. I do understand we are all different and one size has never fitted all which for some reason those supposedly in charge never seem to understand.
Thank you in advance for reading my post and hopefully someone here can make sense of it.