iPhone X poor cell phone performance
Two other threads on this issue existed in the Apple Community Forums but I can't find them to see if they've moved towards a resolution.
It was immediately apparent when I began using it two weeks ago that iPhone X's cell phone performance was very weak compared to the iPhone 6s Plus that it replaced. After a half-dozen dropped calls and many instances in which I could not make a call - all in areas where the 6s Plus has performed perfectly for two years - I took the phone back to Apple.
While noting that my number of dropped calls was below their acceptable threshold of 20% (!!!) they replaced both the phone and the SIM card. It is no better. I'm at my desk, three bars of signal (as it should be here) and two minutes into a call it has just dropped another one.
The Apple store advised that I could set the phone to use only 3G rather than LTE for calls, but I declined since I don't accept that Apple's latest and most expensive cell phone should be unable to use LTE reliably.
Does anyone have any other advice? Does Apple listen here?! Getting very frustrated with this brick of a cell phone.
Thanks in advance for any help.
iPhone X, iOS 11.2