At this point, we can’t be exactly sure why your iPhone won’t play voicemails. The voicemail you play in the Phone app on your iPhone is called Visual Voicemail, which downloads your voicemails from your carrier in the form of little audio files, similar to the music files you listen to inside the Music app.
1. Checking Your Voicemail on a Cell Phone Access your digital voice mailbox through your smartphone's touch screen. On an iOS phone, tap on the Phone application and then look for a square in the bottom right hand corner of the screen that reads Voicemail.

Order online 24/7. Select a voice actor, enter a script, we’ll record and deliver your phone greetings.
I called customer support. They were not able to fix it and made it worse. Now it rings once instead of three times. They put in a service request and said it would be 1-3 days. Now they say 3 to 5 business days. I don't understand how something so simple could be such a major problem. I just wanted them to change the number of rings to at least 7. Disconnected the 1st of the junction boxes at top of door. Phone line rings after doing this so proves problem is in the home. I then ran a new wire pair to the NTE5, problem then came back, even with the pull out isolation port or whatever it’s called. Then wired direct to the back plate if that’s the correct term, phone starts ringing again.