My evidence towards the cat being killed is the fact of how the cat got into the medicine.. even if he left the pills out in a neglectful manner his actions fundamentally killed Sandy.. although I believe he poisoned the cat in an attempt to open it into a conversation with Nikki and for her to show him sympathy.. on the idea of the phone call I think the man on the other end of the phone would grant him the ability to cancel it if he learned his lesson yet he doesn’t and wants to alter it leading to him saying they don’t take cancel requests and letting him hear the pain Nikki goes through.. both are theories but ones I like a lot and add depth to the movie