I want to turn off default option of “AWstats reporting” but It gave me an error.
Failed to save enabled features : Virtualmin is configured to setup DNS zones, but this system is not setup to use itself as a DNS server. Either add 127.0.0.1 to the list of DNS servers, or turn off the BIND feature on the module config page.
My recommendation would be to follow the instructions in the error message
You can add 127.0.0.1 to the list of DNS servers by going into Webmin -> Networking -> Network Configuration -> Hostname and DNS Client, and add it to the “DNS servers” field.
Alternatively, you can edit /etc/resolv.conf, and add it to the list of nameservers there.
After you add 127.0.0.1 as a DNS server, try disabling Awstats reporting again.