I had the same problem on my Samsung Galaxy Watch. The watch was registered in phone as earpiece device and when I picked up phone call on the phone the audio defaulted to watch.
This is a watch icon in Bluetooth dialog on phone when paired as watch:
View attachment 319288
I've tried several things (reboot watch, reset watch, reboot phone) which did not help.
But accidentally I've tried something that suddenly registered my watch in bluetooth devices as watch and not as earpiece.
I did this:
1. bluetooth unpaired watch in phone
2. watch > settings > Connect to new phone > backup data (scroll down) > Connect using Bluetooth (yes) > pairing reqest on phone and watch
3. now the watch was registered correctly as watch and not as earpiece
Now if I pickup call on the phone the audio goes through phone speaker.
Simple fix here. I had the exact same issue - taking calls would result in the watch being used for voice and audio.
I simply unpaired the watch from my phone and paired it up again. Just took and call and voice and audio we're back through the phone again.
I think it was the latest update which has caused this.
I had the same problem on my Samsung Galaxy Watch. The watch was registered in phone as earpiece device and when I picked up phone call on the phone the audio defaulted to watch.
This is a watch icon in Bluetooth dialog on phone when paired as watch:
View attachment 319288
I've tried several things (reboot watch, reset watch, reboot phone) which did not help.
But accidentally I've tried something that suddenly registered my watch in bluetooth devices as watch and not as earpiece.
I did this:
1. bluetooth unpaired watch in phone
2. watch > settings > Connect to new phone > backup data (scroll down) > Connect using Bluetooth (yes) > pairing reqest on phone and watch
3. now the watch was registered correctly as watch and not as earpiece
Now if I pickup call on the phone the audio goes through phone speaker.