My brother-in-law received two letters from Ruthbridge regarding a debt supposedly owed to Argos Distributors LTD. He ignored the first letter, as he has no knowledge of any such debt. A second letter arrived on the 2nd Dec, in which Ruthbridge were offering a 65% discount, which seemed more than a bit fishy. After looking around the site and seeing other actions taken regarding Ruthbridge, I have sent them a prove-it letter. If they don't stop, what further action is advised?