Sollte auch mit BAPI_USER_CREATE1 anstelle BAPI_USER_CHANGE funktionieren.Read the current data of the user with function module BAPI_USER_GET_DETAIL. Use the LOGONDATA structure as input parameter for BAPI_USER_CHANGE. Clear fields BCODE, LTIME, PASSCODE, PWDSALTEDHASH and set field value of CODVN to 'X'.
Then set the corresponding change indicators in import parameter structure LOGONDATAX to 'X' and call the function module. After that (and a commit work) the password of the user should be deactivated.