Just switched from an iPhone 7 to a X(s) and can hardly make a call from my office at work, where I used to make calls all the time before. My bars keep switching from full bars LTE to 2 bars 3G back and forth every few minutes. I've had dropped calls or calls where connection drops in and out. Apple support tried a remote diagnostic and confirmed there are no hardware issues with my specific phone, and suggested I contact Verizon. No one else in the office is experiencing this issue with Verizon though with thier Apple devices, so its not like a temporary outage or anything.
What version of IOS are you using, 12.1 or 12.0.1?
Perhaps try the downloading the public beta and see if that helps. Apparently it's quite stable. Even if it's not overly stable, what have you really got to lose when the phone is having serious problems. If the Public beta fixes your problem it would be a great sign that Apple is on top of the problem.
A few previous posters have stated the beta has helped their LTE, so perhaps it will work for you.