i ques that confuse here is bit more lowlevel what it seems at first.
from firs post i see Ispconfig's hostname is ubuntuServer.isometric.com, but all references to nameserver points to *.iwebsource.net.
could it be that *.iwebsource.net-servers are your service providers nameservers?
if so, you are trying to control nameservers that are not yours. obviously it is not going to work.
if you have access to somekind of control panel in iwebsource.net or in your domain registrant, you can handle dns from there and forget Ispconfig's dns-part.
or, start using ubuntuServer.isometric.com as NS, and instal another nameserver to somewhere. if you go this way, change domains nameservers from registrant to your ones.