About a month ago, nearly all of my dad's phone calls on his iPhone X began going to voicemail. Oddly, he could receive calls from me, and we discovered that if someone else called and went to voicemail, then hung up and immediately re-dialed, their calls would go through. He spent hours on the phone with various Verizon tech people, all of whom took him through the same list of questions - such as is DND on? is call forwarding on? is your phone on mute, etc. The whole list. No solutions.
Thinking maybe it was something wrong with the phone, my dad purchased a new iPhone XS Max last Friday. Unfortunately, his incoming calls are acting exactly the same way. We spent an hour with another Verizon tech yesterday (after my dad spent several hours with them on both Saturday and Sunday), went through the same drill several more times, including re-setting the phone multiple times, and same result! Last night, the Verizon tech, thinking it must be an Apple app problem, hooked us up with a tech from Apple, who took us through all of the same drills, before sending us on to more technical tech at Apple, who had us try a number of new things we hadn't tried before, but nothing worked after two hours with the Apple techs. The Apple tech then tried to connect us with a Verizon tech again - thinking that everything on the Apple side was working perfectly, and that it had to be some kind of a carrier issue - maybe something with the timing of calls going into voice mail. After waiting hold for Verizon for 25 minutes, the tech hung up on us after we explained our problem. So here we are. And as far as I am able to learn, there isn't any way to change the length of time before a call goes to voice mail.
BOTTOM LINE: Most (but not all) calls go directly to voice mail. Calls from me, or call backs immediately after going to voice mail, hanging up and calling right back, are going through. We are at wits end trying to figure this out. Verizon says it is an Apple problem, and Apple says it's a Verizon problem. At this point, the only choice I can see is to start over with a different carrier and a new phone. Can anyone out there help?