New Dual 4G not working


Oct 30, 2020
I bought f2 pro and it was using global version miui 12 and was able to use 4g on both Sim cards in Pakistan
After flashing it into rom,only sim 1 support 4g now meanwhile sim 2 doesnt support 4g,
If i manually go to sim 2 setting and click on 4g preferred,it automatically looses signal and after 2 minutes,it changes back to H+ which is 3g
if i try to use this code *#*#4636#*#* to manually select 4g lte only,it completely looses signal on that sim unless i changes it back
Can someone tell me how to fix this issue ?I am using miui 13 version of now