I've lost count of the number of times that I've seen posting on the Plusnet forums where TalkTalk make it as difficult as possible if a user decides to leave them to move to Plusnet.
Demanding money in respect of a service they allege was provided to someone months before he was even a TalkTalk customer is fraudulent.
Cutting off his service unless he pays them the money he doesn't owe and only then will they investigate is blackmail.
When you've seen a significant number of posts from someone you get a feel for them - I've no reason to doubt what he's saying. OK he hasn't kept his cool, but that's been under extreme provocation and really ISPs should have people who are able to contain and resolve situations like this.
Plusnet user since November 2001