Forcing 5G only mode on Redmi note 12?

[nitinjs]

Hi

On my Redmi note 12 5G
When I go to settings and change the setting to prefer 5G it switches to 4G sometimes and sometimes 5G (dont know how)

so I went to phone dialer and entered *#*#4636#*#*
there I selected NR only
this should switch to 5G only mode
but the network goes away

any pointers will be good for me,
how do I force my Redmi note 12 5G to 5G only mode?