Gas Usage Explanation?

Just had a gas central heating system installed. In the first week Bulb have stated that I used 18 units and have charged me for 206 kw/hour. What makes it even more annoying is that during the period they have billed me for I did not have access to gas as the system was not installed until 4 days later. If anybody can help explain how this works I would be grateful.

Probably an estimated reading if you haven’t given a reading yet. The estimate will be wrong of course because they don’t know the system wasn’t up and running yet.