abap runtime error DBIF_DSQL2_SQL_ERROR

Hi guys,

when I run my program I got this error:

DBIF_DSQL2_SQL_ERROR

Database error text........: "ORA-01400: cannot insert NULL into

("NAPL"."KUPCI"."MSISDN")#"

my code segment looks like this:

.......

LOOP at itab.

EXEC SQL.

INSERT INTO KUPCI (POZIVNI, MSISDN, IME, PREZIME) VALUES

(:itab-poz,

:itab-tel,

:itab-name,

:itab-surname)

ENDEXEC.

ENDLOOP.

......................

KUPCI is oracle db table (with fields pozivni, msisdn, ime, prezime, )

dbcon connection is OK, what could be the problem??

thanks

nihad