Excessive usage after Smart meter installed

I had a Smart meter installed on 19 August (which didn’t work) and I’ve just received an estimated bill. When I checked their estimation against a meter reading I found that the actual reading was quadruple the amount. In 19 days I have apparently used 14% of the amount I used in the last whole year. Given that it’s summer so no heating involved this is shocking. Obviously I’m going to appeal this. Has anyone else had this problem and if so, how was it handled by Bulb?