Any airline could be substituted into the thread title and I'd be running out of airlines to fly on if I had to think twice about flying with xyz airline because my seat changed on one booking. Having said that, on long hauls on my regular routes /airlines I do like certain seats and the OP did exactly the right thing by checking the booking and identifying early that the seat-shifters had been at work. Good result in the end and hope you enjoy the SAA business class product and service. I still think it's one of the better ones.