Voicemail won't pick up
What would cause my voicemail to not pickup on some incoming calls that say unknown caller? Some unknown incoming calls do go to the voicemail but not all of them. The ones that don't go to the voicemail just keep ringing my phone endlessly. The only way I can stop these unknown incoming calls to stop my phone from ringing is to answer the phone and then hang up. I have no idea who is calling me because they don't say anything when I ask them who is calling and the calls also don't even show up in the voicetools either.