please help!

scarabanja

I recently left my supplier who i have been with for years I also left them briefly for about 4 weeks in 2008 due to somehow getting switched without asking to.
Well they have decided that I still owe them for gas from my original account, this is exactly what they sent me

'I am really sorry to advise you but looking into your Gas account there was a finalled account attached dating back to 2008 when your supply left us before. This account has a final balance of £147.57 that was never paid. It was due to be taken out of your bank account on 16/5/2008 but the payment was cancelled. The direct debit plan has remained open therefore our system has not picked up the fact that this account was not paid. Please be assured with the direct plan opened there were no payments taken since the final bill was produced.'

I am currently going through bank statements versus bills to see how accurate this is but if they are right do I actually owe them? as they have never billed me for this amount, they have always had my direct debit details and they have taken a payment every month since I first started with them in 2007. I don't see how if THEY have made a mistake they can suddenly demand money out of the blue? does anyone have any advice?

cheers