Hi Sweta,
Are you saying that the old one and the new one, which you created, both are in active status?
However, to make the old one OR the new one in-active, go through below thread.
How to deavitave Multi-Level Categorization schema?
Also go through below thread wherein the subject is explained in a very comprehensive manner by experts.
Multilevel Categorization - SAP IT Service Management on SAP Solution Manager - SCN Wiki
Rgds
Hari