Oracle Message ORA-14211 - subpartition bound must collate higher than that of the last subpartition

ERRORsubpartition bound must collate higher than that of the last subpartition
CAUSESubpartition bound specified in ALTER TABLE MODIFY PARTITION ADD SUBPARTITION statement did not collate higher than that of the partitions last subpartition.
ACTIONEnsure that the subpartition bound of the subpartition to be added collates higher than that of the table partitions last subpartition.