Npower rip off

[seamstress]

Hi everybody,
May I start by saying that I used to get my electric from Powergen and my gas from British Gas and the charges were around £270 per quarter for electric and approx. £140 per quarter for the gas which I paid by DD every month without fail and no problems.
Why the thread you may ask?
Well around November last year I was constantly bombarded by telephone canvass calls from Npower promising me that if I switched supply to them they would save me pounds.
At first I resisted totally because I was ok, but the calls were relentless to the point where I said that if you could guarantee that you will be cheaper and provide the same service I would give it a go.
The rep from Npower assured me that they would save me money and so I switched.
I must say at this point that I sent them previous bills from my former providers and they came to read the meters so they were fully aware of my rate of usage and what i had been paying.
All was well untill I received my first bill which to my horror was £740 for the quarter which is approx. £330 more than I had been paying previously.
Of course I tried to contact npower and after going through the normal long drawn out wait and endless automated crap on the phone I eventually got to talk to someone about my plight.
No interest or concern was shown by the npower rep i was talking to and like some demented repeating automoton she kept on saying that. " well you have used that many units and you have to pay".
I told her rather curtly that I wasn't paying that much and i thought it must be cheaper as i was promised.She couldn't help and so passed me on to some other bod, { Zzzzzz another long wait and condecending messages of how important I was }.
Eventually i got to speak to some other chap and when he realized how adamant i was that the bill would not be paid he said he would put the account on hold untill he had spoke to the person responsible for selling me the contract and try to resolve the situation. At this point i told him that i was prepared to pay an amount equal to what i used to pay as a gesture of goodwill untill the matter was resolved, he said this wasn't needed and not to worry or do anything untill i was contacted again.
Nothing was heard for a few days untill i got a threatening letter from their collections department demanding payment or they were sending people in to cut me off.
I have since gone back to British gas who say they will supply me even though i am in dispute with npower but i am seeking advice on what to do with the npower situation.

SOME HELP PLEASE.

Regards Seamstress