I will write here so others can benefit.
First of all you should know a difference between CentOS versions. CentOS 7 is not the same thing as CentOS 6. You need to have an extra knowledge to configure CentOS 7 as they moved it to use systemd. Someone who is using latest Fedora is able to do this. You wrote me via chat about CentOS 6 so it will be easier to find sysadmin.
Next thing to know. There are control panels to configure Linux services. System admin have to know which one you're using or not using it at all. It will be an easy task with Ajenti or DirectAdmin and can be a pain with something else. Most of the sysadmins are able to fix things by just using command line.
Last and most important part. I recommend using CSF - ConfigServer Security & Firewall. It is available as a DirectAdmin plug-in. When installed will add a firewall rule in seconds.
That's it. An easy task for someone experienced with machines running Linux.