Incorrect Information held by HMCR

When trying to register for the Gateway I enter my name, NI number and DOB and get told the information is incorrect. Which I know it is not! When I collected a pension pot about 5 yrs ago Scottish Widows commented that my DOB which was correct in their records, was not correct in HMCRs records, but they wouldn´t tell me what HMCR had. How can I get this corrected? and no I can not provide all my addresses and places of employment since I left school, surely a copy of my passport and maybe something with my NI number should be enough to get it corrected?

Hi Sparks1061 Reeves,
To enable us to amend your National Insurance account to reflect your correct date of birth, please send us a certified copy of the ID page of your British Passport (if you have one) with a coving letter and we’ll get this sorted for you.
Our postal address to send your letter to is:-
HM Revenue & Customs
Individual Caseworker
PT Operations North East England
BX9 1AN
Thank you.