severe disability premium

I have been moved to mid rate care,I am in receipt of income support and incap. I received letter and form asking me to fill in re paying me severe disability premium. Have today received 2 dwp letters, both dated the same. One says Im not eligible the other says that I am and has given me an amount of backdated payment?? I have called the office concerned and the BEL and I am now confused.One says I am because 'we' have my sister has no means test impact on me, but the other says Im not, because I live with someone?? (but not a partner)I live with my sister, who works full time 37 hrs pw, she does not receive any benefits and we have no impact on one another financially. No one receives the carers allowance for me. I received mid rate for day care needs and I am on my own all day.
BUT because I live in her property and we live together they say Im not intitalled to severe disability prem. All I want to know is this right or do I appeal. Will someone please help.

I tried previously to get separaste utilities for the half that I pay. I do not pay her rent as I cannot claim HB. CTB is second adult rebate but these arent included in severe disability anyway or so Iv understood.
No idea what letter is right and neither did Income support but they told me to send in for a reconsideration?? on which one?
DLA have awarded mid rate for day care. I am on my own because my sis is thankfully in full time occupation.
I am unable to cook and clean due to disabilities they know about.
My sister cares for me during the night, and is so exhausted.

Gordon
It would be just my luck to get a recon on the wrong one! if that makes sense too.
Do you think then that I should put in a letter that I want it clarified in writing which of their letters is correct one and also if it is the no increase in IS/sda I want a recon on their decision because my sis is not here during the day and dla award letter states for day care.
Id love to know what their admin costs are for sending 2 letters a time out to each of its customers.
capainf