I've been with them for about 10 years, and I've decided to change as the prices were being hiked up at the end of the fixed period, shopped around and using the data they provided (usage etc) I found that sainburys were offering me the best deal, with £40 cashback.
All fine (this was started back in April) I've given meter readings etc, and I'll be changing at the end of this week.
I get a phone call this evening, with some scottish power bloke being all nicey nicey with me, trying to get me to stay. Why do they spout loads of figures at me, tell me they'll undercut etc. But I'll have to pay cancellation charges with sainsburys which they'll refund etc etc. Then when he realises it's not going to be easy to get me to change, (because tbh I can't tell from what he's saying whether I am going to actually save money, and I'm fed up with paying so much that I'm in credit even in the winter) he tells me that he's just trying to save me money and hangs up on me.
He phoned me ffs 
and breathe