Hey there @Elize, thanks for reaching out to us and a warm welcome to the Virgin Media forums.
I'm sorry to hear your parents landline has gone off.
Let's see how we can resolve this.
Have you been able to try another phone?
Are you able to take out all the cables and place them back in?
How are they connected to the landline - is it through the wall socket or a Virgin Media router? As this is the way the majority of our network connects to the landline services.