Thank you for all your input. I tried using trunc function which allows me to insert and update cust table without any error but it does not insert or update cust_interface table.
How do you use the trim function?
here is the description of the tables as requested by the forum:

SQL> desc cust;
Name Null? Type
----------------------------------------- -------- ----------------------------
C_ID NOT NULL VARCHAR2(15)
INST_ID VARCHAR2(15)
PAYROLL_ID_NUM VARCHAR2(25)
COMPANY_NAME VARCHAR2(50)
SALUTATION VARCHAR2(7)
F_NAME NOT NULL VARCHAR2(25)
MI VARCHAR2(1)
L_NAME NOT NULL VARCHAR2(25)
SUFFIX VARCHAR2(7)
EMAIL NOT NULL VARCHAR2(50)
BIRTHDAY DATE
REFERRAL_TYPE_CD VARCHAR2(25)
FOLLOWUP_FLAG NOT NULL NUMBER(1)
SSN VARCHAR2(11)
USERNAME VARCHAR2(25)
PIN VARCHAR2(25)
PAYMENT_INFO_ID NUMBER(10)
HTTP_REFERER VARCHAR2(128)
SALARY NUMBER(8,2)
DOWNLOAD_ID VARCHAR2(25)
BACKEND_ID NUMBER(10)
ACTIVE NUMBER(3)
CHANGED_BY NOT NULL VARCHAR2(25)
CHANGED_DATE NOT NULL DATE
LOOKUP2 VARCHAR2(15)
LOOKUP3 VARCHAR2(15)
ACTION_CODE VARCHAR2(15)
PAY_FREQ VARCHAR2(15)

SQL> desc cust_interface;
Name Null? Type
----------------------------------------- -------- ----------------------------
C_ID VARCHAR2(15)
INST_ID VARCHAR2(15)
F_NAME VARCHAR2(25)
MI VARCHAR2(1)
L_NAME VARCHAR2(25)
LOOKUP2 VARCHAR2(15)
LOOKUP3 VARCHAR2(15)
ACTION_CODE VARCHAR2(15)
PAY_FREQ VARCHAR2(15)
ADDRESS_ID VARCHAR2(15)
ADDRESS_TYPE_CD VARCHAR2(25)
IS_DEFAULT NUMBER(5)
STREET_1 VARCHAR2(50)
STREET_2 VARCHAR2(50)
CITY VARCHAR2(25)
STATE_PROVINCE VARCHAR2(25)
ZIP VARCHAR2(11)
COUNTRY VARCHAR2(50)
COUNTY VARCHAR2(25)
INSERT_TYPE VARCHAR2(3)
TIME_STAMP VARCHAR2(25)