Going forward you will be charged an administrative fee of 50.00 USD for every ticket you open outside of the above referenced ticket.
That is absolutely disgusting behaviour. I was just in the process of joining Inersango, but thought I'd do a bit of research first, thank god I did; I will not touch this service with "customer support" like that.
I'm certain, under law, they can't charge you a fee, at least not that much, for support if you are a customer, especially as they don't mention this in their Toc.
Sounds like they are trying to keep your money and scare you away from sending them any more tickets.
If I was you, I would certainly look into going to a small claims court and demand compensation. It's a case which you will not be able to loose, plus they'd be liable for the court costs.