Thanks for reaching out to the Apple Support Communities! It sounds like you are having an issue with hearing the other party when on a phone call and I am happy to help out! Take a look at this article with the steps to follow If you can't hear a person on a call or voicemail or if the sound isn't clear on your iPhone. This article will give you the best steps to troubleshoot your issues, along with what to do if the issue continues.
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