Talktalk, probably all telecommunication companies as well.
Moving house so changing from Talktalk to BT. Place my order with BT and tell Talktalk, they do a very nice deal so take it and cancel my BT order. I then get a call a few hours later from Talktalk, I'm sorry to say that we cannot provide broadband to the property you are moving to. WTF? You just took the properties details and didn't even check if you could provide the service you just sold me.
So I called BT and tell them that Talktalk are idiots and I would like to continue with my order. It's canceled (rightly so as I asked) so I have to re order, that is the key bit here. As it is over the phone they wont honor the online deal but dont tell me until the end of the order, so I have to cancel for the second time today BT just so I can order it online tomorrow to get the 'online' deal.
Well over an hour of my life wasted that I wont ever get back.