Hello bqueiros,
From your post it appears you are having an issue with Bluetooth disconnecting during calls.
If there is a case on the iPhone, we would suggest removing it and testing to see if the issue continues.
Go ahead and tap on Settings >general > CarPlay. Tap on the name of the stereo from the car and tap "Forget This Car". Restart the iPhone and the car stereo. Connect again and see if the problem remains.
Next, try tapping Settings > General > About > Name. Change the name of the iPhone and try connecting to the car again.
If it continues to disconnect, tap Settings > General > Reset > Reset Network Settings. This will erase all current saved settings, including Wi-Fi passwords, preferred networks, and VPN settings, so be sure you have this information before doing this reset.
Have a good day.