The following code creates Sap Customer Classification using BAPI Function :
report zcustclass.
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* wwww.developerpages.gr
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data : l_return type TABLE OF BAPIRET2.
CALL FUNCTION 'BAPI_OBJCL_CREATE'
EXPORTING
OBJECTKEYNEW = '0000999999' " Customer code
OBJECTTABLENEW = 'KNA1'
CLASSNUMNEW = 'XXXXXXXXXXXXXX' " Class
CLASSTYPENEW = '011'
TABLES
RETURN = l_return.
CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'
EXPORTING
wait = 'X'.