I have a medium instance XXXX.tklapp.com. Then I created a small instance from the backup I made with XXXX.tklapp.com and gave a hostname YYYY.tklapp.com to my small instance. After a while, I decided to delete my XXXX.tklapp.com instance and still keep my small instance YYYY.tklapp.com. I assigned the hostname XXXX.tklapp.com to my small instance and released and deleted YYYY.tklapp.com hostname. 

But whenever I stop and start my small instance, it still uses YYYY.tklapp.com that is already released and deleted so I have to manually release and delete the hostname YYYY.tklapp.com again and attach the hostname XXXX.tklapp.com. 

This only happens to an instance which is created from a backup made by a different instance. is there anyway to permanently release and delete the instance name and change it with another hostname?

I would appreciate any help or solution to my problem.

Thanks