Honestly, this has been going on for months and just hoped sooner or later an update would resolve it after resetting the network settings and voicemail application did not resolve the issue.
It isn't tied to a specific location, or any particlaur building. People have called and left voicemails while I am at work, home, or travelling and the voicemail doesn't come through until some time during the night. As in, they will call, I have nothing voicemail wise no matter how many times I refresh the visual voicemail, or reboot the phone. When I wake up in the morning, I will have a notification that I have a voicemail.
There has been no issue with making, sending, or receiving calls and texts. No issue with data connections. I do not receive a voicemail notification when on Wifi, or not on Wifi.