A. 1. Check your network signal strength. If it's weak, try moving to an area with better reception. 2. Go to Settings > Network & internet > Mobile network and toggle Airplane mode on and off to reset the connection. 3. Clear the cache of the Phone app by going to Settings > Apps > Phone > Storage > Clear Cache.
B. 1. If the issue persists, try resetting your network settings by going to Settings > System > Reset options > Reset Wi-Fi, mobile & Bluetooth. 2. If you have a case on your phone, remove it to ensure the microphone and speaker are not obstructed.