Voicemail not working on Lumia 520

I had straightalk for a couple of months now. The only thing I cant figure out is checking my voicemail. When I call the "voicemail number" it directs me to leave a message. What can i do about this
https://straighttalkwirelessforum.com/
https://straighttalkwirelessforum.com/viewtopic.php?f=6811&t=1270074