Many phones have poor audio quality.
It is virtually impossible to lip-read on a phone. This page shows some ways to improve the sound from a phone to help to make up for the lack of lip-reading, and better audio quality helps with word discrimination. The best we can do is to beef up the sound from a phone by electronically coupling it to hearing aids. It also helps by making the signal much stronger. I will show some of the ways I have used to listen on the phone and some devices I know about only by reading their description in catalogs.