For enhancement of its usage time, Gear S turns off the modem when connecting to Mobile Device via Bluetooth. As a result, Gear S doesn’t receive a call or message.
However, if you want to receive a call or message on your Gear S, please set the Use mobile networks option to Always on.
Follow the path below: Tap Settings > Connections > Mobile networks > Use mobile networks > Always on
Use mobile networks option will now be turned on. Please note that this will increase battery consumption.