One of my regular readers is someone from an Ambulance Control, she left the following in my comments section about why we on the road tend not to see too many hoax calls.

We do get a fair number of hoax calls in control. Most of them can be spotted a mile off, however, and consist of someone under the age of 16 requesting police, fire and ambulance for some unfeasible event. They usually hang up when you read them back the address they are calling from, or, if they are in a call box (which they usually are) tell them to "look up at the 'security camera' in the box so I can see your face" or "the doors of the phone box will now lock automatically - the police are on their way to catch you for making NAUGHTY HOAX CALLS". Obviously, you have to be 100% sure that it is a hoax before you do this, otherwise someone will die and then you will get the sack.

I also spend a fair deal of time when working on the dispatch desks calling back suspected hoaxes from call boxes until a member of the public answers and confirms there are no dying individuals lying around that we ought to be attending to.

One or two do slip through the net, though. There was an almighty ruckus when some really "funny" people decided to tell us that someone had fallen down the stairs and then given birth to her sixth baby on the spot. A whole fleet of ambulances and midwives turned up to find a bunch of sniggering teenagers on the doorstep and no sign of any woman or baby. They didn't even have the sense to give a false address. One of the midwives rang up and shouted at me for half an hour.