Nintendo has released additional information regarding its Nintendo Switch Online App and its Voice Chat service.
According to the FAQ listed on their support page, the Voice Chat functionality cannot be used when visiting other applications on your smartphone device, and will only be available once connected to the Nintendo Switch Online App.
The voice chat will disconnect while you’re talking on the phone or using another application, but your voice chat will restart in the same room once you open the Nintendo Switch Online application again as long as the game session is still ongoing.
Source: Nintendo
