Remember they also upsell Sky channels as well..... I doubt very much the call centre are given specific information on their products either, only what is on the script. In all cases it's best to do your own homework before taking any subscription.
In your case you are right, I never said you wasn't. And you should be able to cancel without penalty, as TNT's website is just plain wrong. I'm not having a pop at you, just simply explaining that the call centre staff will not have "inside information", just the script they have in front of them.
PS. I'm an ex subscriber to BTTV/EETV and I don't have any sort of TNT subscription. And the "recognised expert" is not something I asked for, just interested in the service and try to help when I can (being an ex subscriber).