Luke has just been caught by Jen breaking and entering into her family home. When she sees Luke, Jen suddenly leaps up and pins him to the ground. Luke's in serious trouble and he knows it. If Jen calls the police, then he'll be outed as a shadow child, and that will mean certain death.
So he pleads with Jen to let him go and in the process inadvertently reveals himself to be a shadow child. Jen is also a shadow child, and so it's not in her best interests for her to call the police.
Even so, the burglar alarm in Jen's house has gone off, and the last thing Jen wants is to attract the attention of the security guards that her father has hired to look after the house.
With that in mind, she picks up the phone and calls her father, telling him to contact the security company and cancel the alarm. Luke can't believe that Jen, another illegal child, has used a phone. He's never used a phone before, because his parents have always told him that the government could trace calls and also tell whether the voice on a phone line belonged to someone who was allowed to exist or not.
But Jen scoffs at the very idea. In fact, she laughs when Luke says that she can now be found just from the phone. She replies,
Everybody knows the Government's not that competent.