Text - We need to verify your identity to continue with your claim

Hi - My first post here and a little unsure how this all works.

I spent 3 hours on the phone waiting in a queue and being passed between departments. When I finally got through, I was told that I had failed to pass identity checks and though they would take my application, I would need to call the general enquiries line after to prove my identity.
Eventually I completed PIP1 by telephone and requested that I do PIP2 online.

When I called the general number, I told them that I was calling to do an identity check. I was then told that my PIP2 form was being posted. I said that sounded wrong, and they said they would transfer me to another team to do the ID check and to change my application to online. After waiting another 30 minutes, the music changed and I found myself back on the main number menu options once more.

Whilst waiting I noticed that I had already received the link to do PIP2 online (before I even made the call) so clearly they got it wrong about sending a paper copy. Eventually I hung up as there was no answer after 50 minutes.

Two days later I get a text:

"We have received your PIP claim. We need to verify your identity to continue with your claim. If you are having difficulty with this, call us on 0800 121 4433 between 8am and 5pm. We will not progress your claim until your identity has been verified."

I've been on all of the links and I can't find out what documents to send or where to send them. I followed the login link, but I can't upload any documents there - It's just the PIP2 questions.

So do I need to call that number and spend another hour online to find out how to verify my identify?

It seems crazy, as DWP are already writing me letters about other things, to my home address, where I have lived for over 50 years.

Thanks in advance for any advice.

Steve.