Who I have the same questioned this topic

I have searched a lot to try to find information about this and can't seem to find a reliable answer anywhere.  How many messages does my voicemail box hold before it's full and when it gets full, will I get a notification at all so that I know to delete messages?  If it matters, I'm on an iPhone5 that supports visual voicemail but I don't pay extra for it, it just comes with the phone. Thanks!