How to activate 4G in IPhone Xs

After the latest update in Iphone Xs, iphone stopped showing 4G and LTE. I live in remote area and most of the time I was connected in 4G, while on city automatically changed to LTE or 5G. Now I don't have cellphone phone access, I keep paying unlimited Internet and I cannot even use at all. How can I revetr back IOS system or bring back 4G? At this point my cellphone is useless. I tested in spared Android and it connects to 4G, even 3G. Need help... Thanks.. I tried contacting provider, answer is that Apple blovkes with update and the network company cannot do anything, only manufacturer. I received last credentials and 4G is still not showing. My friend did not updated iPhone X for year and he has access to 4G with same network provider.