When calling a deaf person, you may need to call a relay or translation service, meaning two phone numbers. Virtually no company, even those with a "notes" area have an established protocol for this. And many just don't have even that.
And no notes is a huge pain. You know how it's a pain in the ass to get the cable/Internet guy to come at a convenient time? They often insist on calling first to ensure their trip isn't wasted. Now imagine you're deaf, and the guy calls every time, and he doesn't use a relay/translator, and never actually communicating... He never comes.
God it has to be annoying sometimes. It was for me and I was getting paid for those calls.