Hi Lynsey, could it be that there is confusion over which meter supplies which flat? But even if you are using another's meter it should never register such high consumptions. It does seem that you need to get SP to call back the installer and revue the situation, 250kwh in a couple of days is ridiculous and the customer servicer who told you it was possible was talking rubbish. Could it be that the meter you are reading is a check meter for the whole block of flats? That could make sense. Somehow it has got linked to your account? It sounds like a really big mistake has been made by the installer.
If the App is giving crazy results you can ignore it, a lot of people say the same. The meter itself is probably working correctly and the App will get sorted out soon.