This is strange. The cabin crew usually wait till boarding is complete before switching people around, especially in Y. It's easier in J where the cabin tends to fill up faster. If it's related to a seat issue, the CSD gets involved (or is at least consulted). Seat changes initiated by the cabin crew are rarely unilateral decisions.

While I appreciate that the OP was trying not to be a hassle during the boarding process (one of the busiest times for the crew), I would've politely but firmly pushed for the matter to be escalated before doors closed. It's possible the CSD and ground crew had no idea this was going on, and the FAs were taking advantage of the OP's docile nature.

It's also strange how quickly the decision was made to move the couple to the OP's original seats. How did the crew know it couldn't be fixed if they only tried resetting after takeoff? Something just doesn't add up here.

As for the post-flight dealings with customer service, the OP's experience is unfortunately par for course.