When calls drop or sound terrible, here's what to do. If calls sound muffled or metallic, cut out intermittently or are drowned by background noise, you can take steps to fix the problems. Most of the time, the causes are poor signal strength, outdated carrier settings or physical barriers like walls or metallic veneers on glass.
First, check your volume and speaker output. Next, glance at the signal bars. If those are low, move toward a window or more open space. Voice Isolation is available on the iPhone XR/XS and newer, as long as you have iOS 16.4 or later. To activate it during a call, swipe down from the top-right to open Control Center and tap the small Phone Controls banner at the top of the screen. Then under Audio & Video, select Voice Isolation.
Get a better cellular connection by toggling Airplane Mode on, wait 10 seconds and toggle it off again. Switch to Wi-Fi Calling by opening Settings > Apps > Phone, tap Wi-Fi Calling, then enable Wi-Fi Calling on This iPhone. Update your software by checking Settings > General > Software Update. Restart your phone, check the SIM card, test your microphone, clean the speaker grill, and try a call without a case.
Source: Engadget · Summarized by HeadlinesBriefing