It’s been a while since I haven’t written anything in particular; But, That’s life :)
Anyhow, when you make a change in debian network interfaces through
/etc/network/interfaces, no matter how hard you strive, you would not be able to force it to load newly assigned IP in place.
Here is the trick: Just flush previous IP using following command and restart your networking.
# ip addr flush interface-name # systemctl restart networking
interface-name needs to be replaced with your interface name.