Incorrect first name on Personal tax account (and NI letter)

Hello, My first name is registered inconsistently on: 1) my pay slips (correctly recorded as a combined name in 1 single word, as for my passport) 2) my personal tax account (only 1 of the 2 names that form my combined name) 3) my NI number (my combined name in 2 separate words). I'm not able to correct the name using the online form as it seems that it's only for name 'changes' not for corrections. How can I correct my name on 2 and 3, please? Thank you

Hi,

You can update this online. 

Tell HMRC about a change to your personal details

Thank you.