Check Bluetooth Call Permission (Phone):
Settings → Bluetooth → Tap your Surface → Make sure Calls / Phone audio is ON.
Re-enable Calls in Phone Link (Surface)
Open Phone Link → Settings → Features → Calls → Turn OFF → Close app → Reopen → Turn ON again.
Remove & Re-pair Bluetooth
Delete the Surface from your phone’s Bluetooth and vice versa → Restart both devices → Pair again.
Check Focus Assist (Surface)
Settings → System → Notifications → Make sure Do Not Disturb is OFF.