Accessibility Question

Hi there, Apologies for such a long post.

I have an employee with autism who let me know it can be really difficult to call out for work when they are experiencing a verbal shutdown and was wondering if there was a more accessible way to communicate when calling out.

Right now, We use a single phone number to call out because all managers and schedulers have access to it where due to permissions not everyone had access to the same email accounts, and we are unable to create new email accounts.

Normally I would say just text me or email me, however if I am off there is a real chance if the text or email getting missed.

Would it be weird to suggest something like recording a message what he can play into the phone, or having a friend/SO call out on his behalf, or even just knocking 3 times and letting the other managers and schedulers know that it means he is calling out?

Also If you have other ideas l'm all ears.