Mistaken child trust fund URN for NI number.

In setting up a personal tax account earlier this year, I mistakenly used a URN number and created an account with all other details correct, the ‘National insurance number’ now presented on letters and the site itself is inconsistent with my actual NI number which I had lost the letter to initially. It only occurred to me that something might be wrong with the rejection of my believed NI (URN) number by the DWP through SFE. I printed the inaccurate NI letter from my account as confirmation, thinking this would resolve the issue, only then in checking further through an old folder today I’ve found an original NI letter with my actual number on it. I’ll contact the NI enquiries line as soon as possible to try and resolve this, but any recommendation on how to proceed with fixing something like this would be incredibly helpful.

Hi Peter,
In order for us to investigate and rectify, we will need your full details, including your NI number.
Please also provide details of the information you have used to set up a personal tax account with the incorrect details.
You can call the NI helpline on 0300 200 3500.
Lines are open 8am – 6pm Monday to Friday.
However, depending on the level of ‘confusion’ on the record (s) we may need you to write to us at:
HM Revenue and Customs
National Insurance Contributions and Employer Office
Account Investigations
BX9 1AN
Thank you,