Education is key!
Where I work most of what I do is face to face, work on my own or through email. My right hand gal do most of the phone calls for me and she's deaf in left ear (only just found out a week ago).
Most of my direct colleagues, or peers, know that I use email to communicate to do my job. If I cannot understand them on work phone with loud volume then I ask them if we can take to email. I have not had one person say, "No, talk to me," when I explain how hard to understand them.
It was hard to tell people what I need but, now that I do this for awhile, not so hard to put it out there that this is what I need. All have been understanding. Now, if I can only get idjit hearies, that I only deal with once or twice a month, to shut up and stop being ignorant and say ignorant things, life would be great!