You have to configure your DNS so that both wwww. and without www. has an A-record with the ip to your web server.
Also configure your web server to listen to both addresses.
As noted, you need to add an A or CNAME record for WWW
[sdstern@sds-desk ~]$ nslookup romeangeltours.com
Server: 208.67.220.220
Address: 208.67.220.220#53
Non-authoritative answer:
Name: romeangeltours.com
Address: 217.160.0.251
Name: romeangeltours.com
Address: 2001:8d8:100f:f000::25e
[sdstern@sds-desk ~]$ nslookup www.romeangeltours.com
Server: 208.67.220.220
Address: 208.67.220.220#53
** server can't find www.romeangeltours.com: NXDOMAIN
Thank you fellas for your rapid answers. I try to add a CNAME record but it asks me for prefix and a value and I absolutely have no idea where to find these two? Any suggestion?
Thanks
I would strongly suggest you to contact your hosting tech support to help you setting up your A or CNAME records.
Thanks everyone for your support,
I did contact my hosting tech support and they sent me a link to this page: https://codex.wordpress.org/Rewrite_API/add_rewrite_rule which apparently it is supposed to be helpful but again I have absolutely no idea how to deal with this? Any suggestion? I think they still believe this is not a CNAME record problem.
Thanks in advance
It is a DNS problem, not a WordPress problem. You are missing a CNAME or A record in your DNS.