SQL> CREATE TABLE t (
  2    x      VARCHAR2(50)
  3  )
  4  ORGANIZATION EXTERNAL (
  5    TYPE ORACLE_LOADER
  6    DEFAULT DIRECTORY temp
  7    ACCESS PARAMETERS (
  8      RECORDS DELIMITED BY NEWLINE
  9      FIELDS TERMINATED BY ','
 10      MISSING FIELD VALUES ARE NULL
 11      (
 12        x CHAR(50)
 13      )
 14    )
 15    LOCATION ('t.dat')
 16  );

Table created.

SQL>
SQL>
SQL> select * from t;

X
--------------------------------------------------
"\"Taiwan Mobile\""

SQL>
SQL> select replace(trim('"' from replace(x,'\"',chr(0) )),chr(0),'"')
  2  from t;

REPLACE(TRIM('"'FROMREPLACE(X,'\"',CHR(0))),CHR(0)
--------------------------------------------------
"Taiwan Mobile"