On Ubuntu server if you try to edit the resolve.conf file for setting up the resolvers and to make the changes Permanent you can not simply change the configurations in /etc/resolv.conf ….
As after every reboot the server will reset the resolvers.
To make the changes permanent Try putting your change in/etc/resolvconf/resolv.conf.d/base as this file is referred and the resolver configuration on the server is setup based up on this file.
Then reboot the server or try to restart resolvconf service on the server and check the /etc/resolv.conf
To restart resolveconf use the following command
sudo resolvconf -u