The bad news is that a replacement probably won't resolve the problem. I've had an A1901 model go through all the trial balloons suggested by Apple techs, and then be replaced completely, with no improvement. I've had an A1865 model completely erased and restored by an Apple tech, replaced the SIM at his suggestion, and switched to a different case at his suggestion.
None of these changes have resolved the problem... I've got two iPhone Xs that I cannot rely upon, and have started keeping my old 6s with me for times when the iPhone X is failing. (The 6s has always worked reliably, and still does.)
Reading back you'll find that lots of others have also been through the try-this, try-that, replace-the-phone experience without getting a reliable cell phone. Something in the iPhone X has been overlooked by Apple, and a lot of us are waiting for news that they've figured it out and will be redressing the problem for customers like us.