No one can prevent calls from going to voicemail. The spam blockers are designed so your phone won't ring with spam calls, but nothing can prevent them from leaving a message. If you use visual voicemail and you know the vm is from a spam call, just delete it without listening to it. If you are one of those that still dial in to your vm then, sorry, you will have to cycle through those messages to get to your legit ones. The reason the spam blockers send all calls to vm is because the spam blocking mechanism is not perfect and sometimes legitimate calls get caught in the net. Those callers can leave a message and you don't have to fear missing an important call, such as an appointment reminder, your cable company calling your back or some other caller that uses anonymization for whatever reason. Let's say you have do not disturb on to only allow calls from your contacts through, but you are waiting a callback on a job offer. That call gets caught in the spam filter or is blocked by dnd because they are not in your contacts. Would you rather get the message or not and then not get the job? I don't know about you but I find that less and less spammers are actually leaving spam messages. When my phone blocks a call, only once in a blue moon does a message show up in my vm. You can always ask your carrier to disable your voicemailbox, but then you won't get any voicemails at all.
