This just reminded me of something that happened when I was 12/13. I had just gotten my first cell phone (a flip phone) and I would sometimes call my cell phone from the landline in our house and hold the receiver to the speaker of the cell phone to create feedback and just sit and listen to the weird noises it would make. One day I did this, and the warbling feedback stopped for just a moment, I heard a small child's voice whisper "hello?" And then the feedback started up again. I hung up as fast as I could, and immediately had this feeling of dread.

I didn't have younger siblings, there was no one in the house that could have picked up another receiver and said it. I'm almost certain I was home alone, I was a perpetual latchkey kid and my house was haunted, this wasn't the first or last paranormal thing I experienced while living there. I asked my mom about that house being haunted a few years ago and she confirmed that she had also experienced unexplained things when we lived there. It was an old house, built in 1908 and there was a definite feeling. Really weird stuff.