This is quite strange. Aren't the radios in the XR and the iPhone XS(for example) the same? I wonder what is causing this as its only affecting one specific model and one specific carrier.
I’ve been having terrible reception on my Xs Max with O2 ever since I started using it back in September. Not that Vodafone was much better. And coverage in my area (Cambridge) is supposed to be good.
I have many fewer problems with the same phone in the US, with Sprint.