Address on Personal Tax account

I need to change the address on my personal tax account, as I now need to register for a self assessment after a few years of not needing to do so. However, when I put in my new address and date, it's giving me an error message that says I can't do it, as I've previously given a later date (I haven't). Then it says to contact HMRC with a link to a page of phone numbers. I've called the relevant one, told it I want to change address, only to be told I can do it online (all by the automated voice) with no option to speak to anyone. How do I contact HMRC to change my address?

Hi,

If you contact us again and state 'speak to an adviser' when asked why you are calling, we can update your address.

Income Tax: general enquiries

Thank you.