Hi
Are the enhancement triggered? Please, check if you have records for your overhead rates in your table KONP for KAPPL = 'KA'. Check your entries in tcode KZS2. For further information check SAP Note 310768 - Costing sheet: Maintenance in production system.
Debug also this coding (and how the other exits are called)
FORM user_exit_berbas TABLES ut_cossa STRUCTURE cossa
USING f_cbase LIKE tkzu1-bkond.
CLEAR ut_cossa.
REFRESH ut_cossa.
IF tkomk-kappl = 'KA'. "Zuschläge "comment by Eduardo: check if it's true
CLEAR sy-subrc.
CALL CUSTOMER-FUNCTION '001'
EXPORTING
i_cbase = f_cbase
........ (and go on)
I hope this helps you
Regards
Eduardo