Intriguing, but can use a few changes.
Overall, this was very effective. I like the timing of when you used all the sounds and music. Timing the audio is very important in suspense build-up, and I think you have it down well.
However, I find something to break the experience. Especially the laugh you use for the evil phone. I found it to be too silly sounding. I think something more along the lines of a slow, little girl's laugh might've been more effective. Also, I felt the head exploding thing was a bit uncalled for. Even if it is important, having the girl go through a bit more built-up fear BEFORE her head goes boom would've made it more effective and unnerving.
I know those are only two things, but I feel that they are important to the video.
Although you did say that it's possible to classify this as dark comedy, so that may have been intentional, I don't know.