Warning: A long meandering post, about multiple things, because my day job is at a relay center, taking calls from/to deaf people.
I absolutely understand his fear of letting a relay operator help him here. Now, obviously this fellow can write in English awesomely, and like any other place my coworkers are great people and (the vast majority are) trying to do their job well, so on paper you'd think it could work... But man, when it gets ugly, it gets ugly. You never realize just how much conversations change when a single "not", "un", or required inflection is left out. You know how us hearing people may misunderstand a joke or reference in text/IM? Yeah. That times twenty, because when texting/IMing, you're trying to take the medium into account. Phone conversations are so trivial to the hearing, we ramble at a million miles per hour and often don't include references to our demeanor in words or tone.
It even matters what state the relay operator is working for at the time, as the laws of how the call must be handled are state laws. In Utah you must read exactly what's typed by a deaf person, even if they speak ASL, and must directly transcribe what a hearing person says, even if the deaf person doesn't speak English well. In California, where many people primarily speak ASL, you can translate from English to ASL, and ASL to English. Of course, for us hearing people it's less translation, more interpretation.
One of the biggest problems I have at work? Phone lines suck. It's hard for us to hear (not to understand the deaf accent of, but literally audibly hear) so many callers, both deaf and hearing. And it's rough transcribing a voice with normal call quality and even moreso if the other connection is bad. I never realized just how bad phones sucked until I worked there. I can go home and use Google Talk on my laptop and it sounds crystal clear in comparison to any phone.
Relay calls work well for saying hi to your mother and (usually) calling up your cell phone provider. You will not be explaining fizz buzz to a potential employer. I love my coworkers, but the first time you say "So you'd use a switch-case statement," they'd write "So you use which case statement q" ("Q" indicates a question,) and keep typing, because asking people to repeat themselves infuriates them, and makes them lose their concentration. And because of honest mis-hearing. You don't know the topic, so you don't know you heard it wrong, so you go on.
Finally, why don't modern cell phones handle TTY calls? Turn the phone landscape, put a scrolling conversation banner at the top and the keyboard at the bottom. You'd think it'd be cake. Anyone know what the problem is there? If nothing, then someone get on that, make an app. Make yourself some money. Just credit me as an inspiration. ;)