Fb Confusion

[Smowball]

I just can't see how to change something! I have my own FB profile and in that I also have a group relating to work and also another work page I manage. The page was never set up by me - but by another company who used to run social media accounts for companies. When I was asked to take over managing the page last year I managed to get hold of this company and I can't remember how we did it but somehow she changed the admin or whatever from them to me. So now when I post on this page even though it's a business page it comes up as me posting.
Obviously we don't want that. So the business has set up an actual business FB profile but FB won't approve it as they say a page already exists under another profile - me I assume. They've sent business cards, letterheadsetc to prove it's really them but FB isn't budging. So how can I change the admin, username on this page to the business as I can't see any way of doing it even though it was done last year!
Am getting so confused.