Not easily. Most sites that say they can do a reverse number lookup for a fee, can not handle requests for cell phone info.
Why not just call the number, (block yours with *67 in front of the number) and see who answers
Who is the account owner? Who pays the bill? If yo are seeing this number on the bill, then I would assume it is you. You have a right to know what's happening on the bill you are paying.
I realize there is likely a situation that would make it difficult to ask the person whose line it is, but that would be the simplest solution. Just ask.