Hello and welcome to Apple Support Communities Sandiertx,
We see that you're having an issue with the audio on your iPhone during phone calls. We know that it is important to have your iPhone working properly, and we'd be happy to help.
Let's begin to make sure that you're using the latest version (13.5.1) of software on your iPhone. Next, go to Settings > Bluetooth, and toggle Bluetooth off, and restart your iPhone.
Update your iPhone, iPad, or iPod touch
Restart your iPhone
Once you've restarted your iPhone, toggle Bluetooth back on. Then delete all pairing records found in Settings > Bluetooth and rename the iOS device in Settings > General > About > Name. After this, trying pairing your devices again and test to see if the issue remains.
Let us know how this goes.
Have a great day!