At the door
This food delivery service sends people messages saying that someone is at the door. When you open the door and realize that no one is there, you check your phone again and see that it was all a joke played by the company in an attempt to get you to order food.
There are easier ways to get people to use your service, you do not need to trick them and send them a prank message. If our food delivery service did this to us regularly, we would stop using them altogether. When we are hungry we will let you know, do not bother us.