Overpaying massively

I am sure there is a big problem as I am currently paying £599 per month and had message that I should increase my monthly payment to £934. My account is in credit by £3313. My house is a 4 bed detached and only myself and wife reside here as kids all left some years ago. My neighbour in same type and build of house pays £180 with OVO. My central heating and hob is gas but the electric cost is much higher than the gas. It seems stupid that I have let this go on for so long but having read over the last couple of years about soaring energy prices when I was told by Bulb a year or so ago that they don’t see a problem I put this to the back of my mind.

I’m in the same position but not in credit as much as you.
i cant seem to find an option to claim back the credit amount which is annoying.