Hi @D Giri,
Although, you have integrated with the LDAP, you still will be able to use local user accounts in ambari, hence you can remove all the external(LDAP) accounts in ambari and recreate the required accounts, which will work as it expected and fulfill your requirement.
if still need to remove the configuration details, you can do ldap-setup with dummy ldap server url ldap://example.com:386 and --ldap-save-settings option to Save without review for LDAP,
which ensure that user can never be sync from any server( only local accounts will work ).
Hope this helps !!