Anecdotal only, but in the 15 years that I've used cell phones, I was never once unable to make a phone call when I had full signal bars. That is, until I switched to Google Fi on my Pixel XL 2. After the switch, I was constantly missing calls and messages. And needless to say, download speed was abysmal. Tried customer support, swapping SIMs, resetting phone, and all that, to no avail. Switched back to Verizon after a month and never looked back.