PIP1 completed over the phone?

Apologies if I am asking a question on the forum incorrectly; I have subscribed for many years but never been brave enough to ask a question!
My husband has been claiming DLA on an indefinite basis for about fifteen years for physical and mental health difficulties. He has recently been invited to claim for PIP. I notice that the first part of the claim has to be done over the telephone. It has always been part of his disability that he has been unable to talk on the phone because of his mental health difficulties and he is unable to hear properly due to inner ear surgery many years ago. I plan to call the DWP to start the claim but I would like to know if it will be possible for me to answer the questions on his behalf or if they will send out a PIP1 form without penalising him? Is there a point of law to quote if they say he must speak to them on the phone? Every claim he has ever made has said that he cannot use the phone because of his mental illness. Apologies for the essay. And thank you!

Thank you Gordon! What a novice I am lol.
I have the PIP Claim Guide at the ready for easy reading