They can't stop you paying by quarterly DD you know. They can't stop you changing suppliers either, it's slightly harder on E7 and E10 tarriffs but not impossible.
If you are sensible with the heating and water heating there's no reason it should be that high.
If its newbuild are there any solar panels or ground heat pumps?.
We had electric only in one house, to keep the bills down I;
Only heated the water to 55c for twenty minutes a day, less often in the summer. A new tank should hold the temperature for 24hrs.
I lagged all the pipes around the tank that got hot with thick foam. Your builders only obliged to lag the first metre.
I only heated the rooms we used, so lounge, bedroom and kitchen. There was no heating in the bathroom.
I'm assuming you are fully insulated because its new but simple things like brush draught excluders on the door and thermal curtain liners have kept us much warmer since we had that house.