I recently finished a contract at Tiscali in the Billing department. Tiscali was pulled up in the BBC news for having such a horrendous billing service.
People were billed twice, not at all, wrong products every possible method to get it wrong, they did.
The problem is that Tiscali is made up of so many ISPs across Europe with all their own legacy systems, bringing this lot together was a task and a half.
An utterly nightmare organisation. As a piece of advice, just go for the free service - don't touch anything that requires billing.