Hey, same problem here!! Except i'm on Tmobile. I too just upgraded to the LG V20 after being an Samsung S6 user. Was really excited about the LG and like you, I do love the phones screen, camera, browsing experience etc, but am having huge issues connecting. It's not just connecting calls but also connecting to the internet and also receiving MMS and sending pic texts. It's also not very intelligent when it comes to switching from wifi to network internet or calls when it needs to.
The samsung s6 and previous generations I've had on Samsung were brilliant at getting the user connected if wifi was on but signal was poor...it would route the most optimal signal to make sure you got the end result. With the LG V20, IF wifi is turned on and the wifi signal fails it doesn't catch a wave on the network to get you connected and just craps out if you try to make a call. Even with wifi turned off, I would say about 40% to 60% of my call initiations DO fail and are unable to connect. Sometimes I can make call after call with a perfect win rate with no issue and then out of no where it will begin a fail streak again. So this is VERY frustrating.
I got the phone about 10 days ago and I'm still within the 14day return period with tmobile. I was hoping that the issue was the phone was just a lemon and would get the LG v20 again but I've read too many other users experiencing the same issue. Although tmobile claims this is not a known problem. I went a few days ago to talk about replacing this and they suggested they first make some adjustments and switch my sim card out. They also changed a few network settings like turned roaming on. It seemed to work fine for a few calls and then once more started the fail streak.
I just called tmobile to explain my frustration and that I do not expect to be charged the $50 restocking fee and that I want a brand new phone (other or LGv20) since this issue has been happening right from the onset of the new purchase. They're honoring the $50 wave and invited me to go get any phone of my choosing.
Overall, minus the connection issues It's a great phone...but again, worthless if you can't connect obviously. I'm attached to this phone simply because of the screen size being 5.7 compared to other phablet like devices that are 5.5. But with the call connectivity and also that you can't simultaneously attach more than one image in a text thread....like you can only attach one image at a time and then go back and repeat the attachment function again...i mean what's that about!! like build the UI right! Why leave something like this out!?
So I'm inclined to get the iphone 7S plus or the samsung s7. The samsungs have all been very good to me when it comes to dependability on network & wifi connection. Appreciate any feedback someone else might have