We filed a patent. It was approved but then the office action was double patenting. 

To respond to this office action do I need to sign power of attorney?


Is there data base for for patent lawyer customer numbers in US?
What rights does power of attorney give ?

" I hereby appoint the Patent Practitioner(s) associated with the following Customer Number as my/our attorney(s) or agent(s), and to transact all business in the United States Patent and Trademark Office connected therewith for the application referenced in the attached transmittal letter (form PTO/AIA/82A) or identified above. #26344"

How can I find who is behind this customer number. Different name appears for U.S. Patent Office Registration ID with this number.