This rooooocks!!! I love it... What did Echo do!?
I think someone needed her help and gave her a call. But because Echo didn't pick up it was their last call. Maybe they were being threatened by external forces. Maybe they were suicidal. Bottom line is that Echo didn't know how important that call was and decided not to pick up. Now she feels guilty for it. That's what I think. Again, I wanna say awesome game. The sound direction made it feel super immersive.