S21 Ultra 2 connection issue

[hessa Mohammed]

on March 27 2022 i did updates for my mobile S21 Ultra - Dual SIM card and noticed since that time the connection is really poor. 

Whenever i call anyone suddenly the phone line cut.  or i can hear people voice and they cannot hear me

I want to call to someone.  Message appear that stating "network is not found"

the internet connection always is discount 

I have change the two sim to my other  phone S9 plus. I did not face the above  issues.

Please assist on this matter