People on the other end of my calls complain that they can't hear me clearly, or that my voice sounds muffled. I've tried different locations, but the issue persists.

If the problem persists across multiple devices, contact the support for your phone, headphones, or car manufacturer.

Try connecting your phone to a completely different Bluetooth speaker or headphones to isolate if the issue is with the phone's hardware.

Ensure no other devices are actively trying to use the same Bluetooth audio profile on your phone or the car stereo.

On your phone, 'forget' both the headphones and car from your Bluetooth settings, then re-pair them as if they were new devices.

Consult the manuals or manufacturer websites for your headphones and car stereo to see if firmware updates are available and how to install them.

Check for and install any available operating system updates for your phone, as these often include Bluetooth driver improvements.

Ensure your phone is within close proximity to the Bluetooth device, especially in the car where the receiver might be further away.

Try using the devices in a different location with fewer potential sources of interference (e.g., away from microwaves, other wireless devices).

If using a thick or insulating case, remove it to allow for better heat dissipation.

Keep your phone out of direct sunlight and avoid leaving it in hot environments like a car dashboard.