Local and Global IP address for IPv6

Hello @ashok.tx ,
I am able to set the new IP address at boot time by creating a service and running it at boot time. But I am facing a new issue.
When I set a new IPv6 address, the old IPv6 address also persists. I am deleting the old IPv6 address using ip command.

ip -force -6 addr del fd00:db8:21:444:406e:8dff:fec1:6fe5/64 dev eth0

But the old IPv6 address reappears after reboot. I created a script in /etc/profile.d/ to delete the old IPv6 address, and tried to delete the IP at boot time using service but it reappears even after deleting it on bootup.
Is there any way we can delete this old IPv6 address permenently?

Thanks,
Prathamesh Kulkarni