The Utility Warehouse

We recently agreed to swap our electricity supply to the Utility Warehouse, they offer a "Triple Guarantee" that they'll be cheaper than our regional provider who we were with so it seemed a good move. At least until we got written confirmation of their pricing and they were more expensive. After a very long phone call where they tried to convince me that I was wrong they finally accepted the simple maths and agreed that they were unable to beat our regional provider. The mighty "Triple Guarantee" seemed a little worthless. Needless to say the agent I had gone through (a friend) was less than pleased and refuses to believe that they aren't cheaper, ignoring the facts and telling me that I just need to "believe" in the product. Madness really. To be honest I'm a little concerned about him and his new venture, the whole thing seems to built around guarantees and promises that they are unable to keep. He seems a little taken in by it all. I just wondered if anybody had any similar experiences with this company and their guarantees.
I've just used one of the comparison sites recommended by MSE and have saved about £200, so all's well that ends well I guess.