In the background of your vocal track, lay down a track of white noise or TV static. Keep it very quiet. When the character speaks, the static should spike slightly. This simulates the character interfering with the electronic signal.

You need the voice to cut in and out rapidly.

Leo tried to unplug the Genesis. The cord slithered away like a dead snake. The voice grew louder, leaking into his phone, his laptop, his microwave .

To make it sound dangerous :