This site: www.phonecaption.com is GREAT
It is a free site and provides free captioning to people who are hard of hearing in the US. It's sponsored by the govt and is here to help you in your phone conversations.
Talking over the phone can be frustrating for the hard of hearing...so this site wants to help you and make things easier on everyone. You have a conversation as normal and the person you wish to hear will have their words appear on a screen as they talk. The company provides the captioning to the person who is hard of hearing. The person who hears normally just speaks into the phone as usual.
It's hassle-free and easy to use.