To set up AT&T basic voicemail, from the clock screen press the Power/Home button. Note:NumberSync must be enabled in order to use Voicemail on the device. When NumberSync is enabled, calls to the primary device will be routed to the primary voicemail box. These instructions will set up your Galaxy Watch's voicemail box. To set up your phone's voicemail box, access your voicemail box by selecting and holding the 1 key from your phone.