I don't know if this may strengthen your resolve, but I had a charge put on my credit card statement, which is with Lloyds TSB, for a late payment, according to them. I always pay off the debt within the month, so I was sure they had made a mistake, I checked my previous statements, and sure enough I was right. I phoned Lloyds, and after waiting for ages and getting passed to various people, I was put on hold. I hung up and decided to write a letter. In it I explained their mistake and that because I had taken time from work [i am self employed] to write the letter, I would charge them £10.00 for the inconvenience, and any other correspondence would be charged. I received a reply quite quickly, with an apology saying that the mistake was theirs, and that a refund would be made, and they would also pay my bill of £10.00.
Paul.