To fix the telephony issue, Flash this

(Link)

How to fix BT audio in Android 10?

First, Download audio configured xmls.
Second, go to recovery and place these according to their denoscription.
Third, Restart your Device.

(You can also include while porting.)

Place this in vendor/etc. Don't forget to delete the original xml first.

Place this in vendor/etc/audio. Don't forget to delete the original xml first.

I am very tired