It's null-time

My phone line isn't working. I went to the faults website to check on progress:

You scheduled an appointment for: - null . An engineer arrived at the agreed time, however we were not able to gain access to your premises. Would you like to reschedule your appointment?

I wasn't at home at null o'clock, but it seems an engineer didn't turn up either; no card through the letterbox. Oh, of course, they put a null card through the letterbox...