Advice for a neglected child

There is a small child that cries everyday by the window. I came to know of it two days ago. It seems the father locks the child in the house when he heads to work or leaves the child leaving the child alone. The child is 4years old. It seems this has been going on since December. The child climbs by his bathroom window and just calls out to people. It seems the mother abandoned the child with the father and the father aint much of a father. The child said he had eaten cornflakes the whole day and it was about 4 when I asked him. From 7 in the morning to 6 in the night. He reaches out to people asking them to open the door. It seems the father is abusive aswell as the child said he hated the father and was afraid of him. The room is littered with bottles and smells like a club with a hint of piss. Is there any advice on what can be done about the child.

I tried calling the child protection hotline but it told me to call another number and hanged up then I called the number and the number told me to call itself and hanged up. Which was basically a dead end. So any advice you guys can offer.