Your initial guesses, whatever they may be, are probably wrong.
Following the plot I made my own guesses, including one as to the nature of the message. These were challenged by the plot twist, although there remains a certain connection between what I guessed (and what most people will guess) and what actually is happening.
The problem, to me, is that neither during part one (“The Episode”) nor during part two (“The Twist”) was I particularly impressed with the quality of the writing. To say nothing of part three, which is “The Epilogue” but to me could just as easily be labeled “The TV Time Filler”.
This isn’t BAD…don’t get me wrong. But it’s uninspired, at least as compared to the rest.
It is adequately executed competence, nothing more; ‘Black Mirror’s Contractual Obligation Episode’, at least to me.