Hi friends
Thank you for your asking. Because my device doesn't encounter the same problem with the same firmware, kindly try some stay-at-home troubleshooting tips below:
1. Please try to enter "Safe Mode". If the function works well in Safe Mode yet the issue remains out of Safe Mode, please check on any disturbance from the installed 3rd party apps.
# How to enter and exit "Safe Mode"
https://www.asus.com/support/FAQ/1005163/2. Also, please try "the Factory Reset"
Settings>System>Advanced>Reset options>Erase all data(factory reset)
Please note that once the Factory Reset is completed, all data, apps, settings and personal information will be deleted.
If the situation remains the same after performing the Factory Reset, please bring your device to the repair center for device checking. You can also do some primary checking at home:
1. Test the calling function with speaker/loud speaker/cable earphone/bluetooth earphone
2. Check on SMMI test
Calculator> type ".12345+=">SMMI TEST>Single Test>Speaker Test/Receiver Test/Headset Test