My dad said that he can feel someone walking around him and trying to wisper him something. That time, his mobile stops working(outgoing completely stops). The phenomenon is mostly after 2am in the morning.. That thing even follows him, as he even experienced it when he went for a tour. The thing is completely invisible, but freaking too! Can it do any harm? What does it want!

Your dad has to ask the spirit what it wants, either that or have it completely excorsized from him. It means no harm if it hasn't done any.

Tick

Make sure you have a tape recorder running and maybe you can hear what is said. Has he seen the spirit?