Thank you for your advice! I've been speaking to N Power mostly via e-mails because whenever they call me I'm in work and can't answer the phone. I have it in writing, them admitting it was their mistake. Once an SAR and an estoppel have been sent, what happens from there?

Hi Everyone, I really need some help and advise with an issue that I currently have with N Power please. My partner and I used to rent a small one bedroomed flat, which we moved out of in August of this year and everything was electric, we had no gas at the property. Whilst we lived there all bills made to N Power were made on time and yes they were always high but we just assumed this was normal. On the 14th February 2017 we received a bill from them telling us that our monthly payment has decreased from £94 per month to £21 per month and they also refunded us £559.57 because we were in credit and had been overpaying. We continued to pay £21 per month with no problems until we notified them that we were leaving the property on the 19th August 2017. When our final bill was posted, they said we owe them £1093.40! After getting in touch with their customer service department, my partner and I must have spoken to around 4 different people and none of them could figure out why our final bill was so high, I contacted the complaints department who then looked into this issue for us. This issue has been going on since August now in December they have finally come to a conclusion regarding our bill. They have admitted that it was a fault made by them and that we should never have been given a refund and we should never have had our bills reduced to £21 per month but they still want us to pay back the full amount! I completely disagree with this. I obviously don't mind paying them for the energy we used but why should we pay them back to fix a mistake that was made by them? Please can someone help me as this is the first time I've had to deal with an issue like this and I don't know what to do. Can we fight this or do we have to give in and pay them back the full amount? Any advice on this will be greatly appreciated! Thanks, Michelle