There are a few ways that you can call and leave a voicemail without ringing. The first way is to use the *67 feature before dialing the phone number. This will block your caller ID from being sent to the person you are calling, and they will not be able to see your phone number. The second way is to use a VoIP service, such as Skype or Google Voice. These services will allow you to make calls without using your regular phone line, and you can also set up voicemail so that people can leave messages for you without having to actually speak to you.