I received an electricity bill for £438.51 from EDF yesterday afternoon. It covers the period 22/8/11-13/2/12. Up to now, I've been paying £52 a month by DD. They have kindly informed me they now want to change my DD to
£580 a month! 
Obviously, I am presuming they have made a HUGE mistake and in fact, they mean £58.00, but my heart failed for a few minutes yesterday afternoon, before rationality kicked in. I couldn't call them there and then, as their customer services close for the weekend at 2 p.m. on a Saturday, and it was after that when I picked up the letter.
I am going to call them about it tomorrow, but I am very tempted to make a formal complaint in writing too. I am wondering if I should just cancel my DD now, and tell them I'll pay quarterly from now on, or give them until the end of the week to send out a new letter with a sensible DD amount on there. I shall update you all once I have spoken to them.