What does Unicom mean by missing calls?

If your Unicom mobile phone number receives this kind of short message, it means that your mobile phone package includes or additionally subscribes to Unicom Calling Bao or Unicom Secretary service, and the short message reminds you of missed calls when the mobile phone is not in service area;

If you hear this voice prompt when dialing other Unicom mobile phone numbers, it means that the other Unicom mobile phone number has subscribed to Unicom's incoming call message treasure or Unicom's secretary's missing message reminder service.