Watch voicemail
How do I set up voicemail from my Apple Watch? The phone number is not associated to a phone, I’m using family setup for the watch for my kids.
Apple Watch SE
Watch family setup doesn't mention voicemail as an option with a watch not associated with an iPhone.
Set up Apple Watch for a family member - Apple Support
M1 Mac mini, macOS 12.2.1; Watch, series 5 GPS/cellular, watchOS 8.4.2; iPad Pro 2nd Gen, iPadOS 15.3.1; iPhone 12 Pro, iOS 15.3.1; TV 4th Gen, tvOS 15.3; HomePods, audioOS 15.3 and Airport Express w/ Airplay 2