When I sync a smartwatch with my mobile device, I stop receiving incoming calls.

Google/Apple smartwatches that are synchronized with cellular devices have the option of setting a DND (Do not disturb) mode, which overrides the device settings.
In this case, incoming calls (VOIP only) and SMS messages will not be received by the application.

Keywords: smartwatch, watch, Bluetooth, do not disturb, DND, VOIP, incoming calls, incoming call, not receiving calls, no incoming calls.