Whether you can record your own greeting (also known as “voicemail outgoing message”) depends on your carrier and whether they have their own mechanism in place, or integrate neatly with the iPhone’s native functionality.
Assuming you only care to hear from a handful of people, open your phone’s Settings, and tap on Notifications. From here, tap on Do Not Disturb and toggle it on. Now, you can tap Allow Exceptions and add the contacts you’d like to get calls from.

You may be prompted to input a password if you have any security functions in place. Input your password to continue. If you are still prompted for a password input even if you do not have any security measures in place, all you have to do is type in the last four digits of your phone number.
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.