Just having a little browse around and discovered a great post on Public Energy about how to terminate your contract with Carphone Warehouse without being screwed. It’s referencing their mobile contracts in particular but from the terms and conditions doc at the Talk Talk website, I’d bet it’s the same.
The whole process looks like it’s been deliberately engineered to screw extra money out of their customers. If the security validation is good enough when I buy the phone, why isn’t it good enough to terminate the contract? There isn’t a good reason of course. Even the address you have to send the letter to is full of references and odd PO Box numbers that are open to mistakes to further delay the process.