Logon Trigger Not Getting Updated

There is a xxxxx.sql file in the OS level which contains create or replace trigger script. I modified that file with the code below:

if(upper(USER)= 'U_USER') then

execute immediate 'alter session set current_schema=USER';

end if;

after that, I went to sqlplus
and logged in to U_USER like this
SQL>conn U_USER/U_USER;
connected.

SQL>@xxxxx

some numbers are getting generated if i press enter.

Then i press ctrl +c and get to sql prompt.

I issue

SQL>select SYS_CONTEXT('USERENV','CURRENT_SCHEMA') FROM DUAL;

I am getting the output as U_USER but I must get the output as USER and not as U_USER. Basically the trigger is not getting updated.