I use Tiscalli, and every month I receive an email informing me that a payment is due, and it will be taken from my account on a certain date and time.Whether you pay by Direct Debit or Credit Card, you should have details when payments are due. Have you not received this communication?.
If you have used the service since November 2003, and no payments have been made, then surely you must have known about this before now. It is no good saying that Tiscali were to blame, unless you have made previous attempts in bringing the matter to their attention. If on the other hand, you have tried to communicate with Tiscali and have had no response, then this would be a different matter.
If the debt collection agency are using threats or intimation methods, then there are laws and safeguards available. Consult your local trading standards, citizen advice or local free law centre for advice.