iphone X: No Signal Bar and blank page for SETTING>MOBILE DATA> (blank)

i am using iphone X. My problem is that there is no "signal bar" (and it keeps on searching) on the top right corner of the screen, even though i can use the sim card and get "signal bar" when transferred to other phone. The network signal in my area is strong.

when i go to setting>mobile data> (blank) the page for mobile data is BLANK.

please help.