The letters that Sky send now when there are line connection problems have been redesigned.
They used to say, something like, Hey You, we know that you are a crook and have deliberately sold your box to someone in Spain but we have got your number matey. So ring us immediately or we will double your bill.
Words to the effect, if you know what I mean.
Now they are rather more polite and go through a series of self diagnosis options that you might not have thought about - including adding in the code for ex-directory numbers (which our Sky installer never did or suggested to us that we had to do). This facilitates an immediate callback to check it is working.
So well done to the Sky customer service team here as they have listened to the complaints about the rather confrontational nature of the original letters. These at least give you the benefit of the doubt that the cause for the failed callback is a problem you do not know about rather than an attempt to cheat Sky.