The concept has potential I guess, but there's quite a bit of room for improvement with the execution. I won't talk about the writing, but maybe I can get into a few things that seemed a bit off in my opinion.

First off, I didn't understand the purpose of those quick cuts and that random fading transition in between during the phone call sequence. Would've helped to have another angle on that too rather than just doing the whole scene in a single close up; hard to hold the viewer's attention like that especially in a case like this where the dialogue isn't supposed to be giving away much either. Maybe have him move around a little while expressing panic, explore the locale a bit?

Another thing with really bringing out themes like these visually is knowing how long you need hold a certain shot, both before and after the character leaves the frame. These are little things that you'll learn with time, but what I really noticed in these three minutes is that you use the camera to just frame the subjects rather than to build the world around them.

Lets look at the sequence with the walk down the corridor for instance. To make the reveal that followed really mean something, you could have built some tension going into it - focusing on the narrowness of the corridor with the walls closing in on the subject, maybe a shot following the subject's feet with every step he takes, a close up of his face as he gets closer, etc - there's so many ways. Remember, you're trying to make the viewer feel with every shot they see - it isn't just the dialogue that tells the story.

The only way to pick these things up is to watch a lot of films and, well, making films yourself. And you're doing that, soo. Good luck!