Don't cancel the DD as it will lead to missed payments, credit rating affected and possible visit from a bailiff. How long have you had the contract as there may be a half price period that has been forgotten. Also there was a price increase on 1st April of between 4.5 and 13% depending on when the contract was taken out. There can be a slightly larger than expected first payment as the date you started the contract is not always the bill date.
Check your bank and see what has been taken, if anything. It's really annoying 3 are having all of these system and customer service issues but that's something that we should not have to put up with.
Finally, if you are in the first 30 days, you may have the option to walk away.
