I pay by variable direct debit (with BG). This means I only pay for what I use each month - no ‘excess’ money sitting in their account. They send me a statement online at the end of the month and they take the amount out of my bank via DD two weeks later. I know what the amount is going to be anyway because I’ve got a smart meter. I started this variable system when, like you, I was informed my fixed DD was going to increase despite being hundreds of £s in credit. When I phoned them to say ‘you’re taking the P … you can stuff it’ I was informed about the variable DD. Prior to that I didn’t even know it existed. Anyway, it works well for me. As others have said, we are the client here and, as such, we’re in control - not them.