My fixed term energy contract ends later this month & I have initiated a switch. The existing supplier has not supplied a bill in the 11 months I have been with them but it is a relatively simple fixed rate tariff & so I am confident that my own spreadsheet calculates what I owe. In fact I calculate that I am currently slightly in credit but by switchover date I will owe about £10. Coincidentally my DD for £60 will probably go out the day before the switch - so they will then owe me £50. Unfortunately the company seems to have a terrible reputation for getting round to refunding credits. It seems their computers systems are in a mess. I have considered cancelling the final DD and settling the outstanding £10 separately - but I understand that this might give them grounds to halt the switch (if they notice in time). So I am considering speaking to them before the switch and making it clear that I am only authorising them to take such an amount as is necessary to clear the account. If they then take £60 & don't refund the over-payment promptly would I then by justified in claiming that the final £60 was not taken in accordance with my instructions & re-claiming it via the DD guarantee?