Hi -.Mak.-
Thank you for reaching out to us about your iPhone. Rest assured that we’ll do our best to assist you.
The article below can guide you on how to troubleshoot your iPhone if you hear distorted sound from the speaker or receiver.
If you hear no sound or distorted sound from your iPhone, iPad, or iPod touch speaker
If you are using AirPods Pro, the article below may help.
AirPods Pro Active Noise Cancellation and Transparency mode
If you need further assistance after trying the steps in these articles, let us know which iPhone model and iOS version you are using.
Also, do you have Phone Noise Cancellation enabled? These details can help us be in a better position to assist you or get you pointed in the right direction.
Cheers!