Mark
Dont except that, if they have got it wrong dont pay it, they will threaten court and all sorts but stick to your guns, if they have cocked up keep going.
I got a total refund on the aaaaaa thing that they do because my rep told me they had canceled it but had not so I was at the back of the book, took me a long time and court threats from them, they even passed it over to a debt collector but I still refused to pay and in the end they canceled the claim and went away.
You have to stand up to them, most people give up and except what they say to them, but what you have to remember is that they are sales people without any brains. Just keep at them.