When I was in Wonosobo

It started when I was in a school trip around Java from my high school, except East Java. I was in Wonosobo when I had a horror experience for the first time of my entire life. I wasn't expect it at first. I arrived at Wonosobo at 9 PM, me and another school team, which there was 8 bus entering the main city of Wonosobo. Its already scary when we waited for the red light turned green light. There was no other vehicles except our 8 tour bus. Which scary the most when we entered the small path an it started surrounded by trees and the road was getting uphill. We actually would visit the colour lake, to see a sunrise at Dieng, and to see a "Anak Gimbal" in there but we weren't had a chance to meet them for some reasons.
So, after a breathtaking trip finally we were arrive at a hotel but I could not really say a hotel too. It was like a Mess because the room wasn't that much, and I was with another 7 person in one room. Well you can imagine that. And our room were in the corner near the wall. So, basically we were in the last room.
My teacher announced us to woke early at 4 AM to see a sunrise in Dieng and see another tourism place in there. So me an my friend Tamara were in the bathroom first, we had to hurry because there like 6 person waited on us to took shower. And while me and Tamara bathing things she said "did you hear something?" And I was like " yeah I guess, is that from the girls outside?" " I don't think so" she said
It was a girl voice-soft and slight serenade our ears. And it came from the left wall and when I realised that we were in the corner and we only had a neighbour in our right wall, I started to think that must be something wrong, and I asked Tamara to hurry finished her things so we could get out from this spooky bathroom. Oh I forget to tell you that the bathroom literally inside the cupboard. And we rushed out from there and yelled who was singing outside, and those girl faces were just "not knowing anything at all" and one of the girls said " we were not singing we just busy with packing and the others are go to another room" me and Tamara stared each other and realised that was a Kunti voice. It was slight and we could not mimicked the soft-slight voice.