When serving customers with hearing impairments, you should ask how you can help by shouting.

There's no need for shouting! Start by asking them how you can help and wait for an answer. They may lip-read and respond to you right away, or maybe they'll ask you to repeat yourself by writing or using an app on their phone. Anyhow, they are used to these situations and will get their message across to you. Photo by wayhomestudio from Freepik.