[Koha] Dewey to LLC changeover

[Mesfin Teshome]

Dear all,            I was asked to help out on changing classification system that's currently in Koha from Dewey to LLC. Changing the classification system from Staff client and changing the itemcallnumber in the system preference to 050ab didn't seem to change the DDC call numbers. Searching the catalog still shows the DDC call numbers. Is there anything more I should do? or is this process not automatic in Koha?

Thank you