Hi,
This happened a few years before. I'm afraid, if I would be able to find the respective post.
But, yes NOC switching flexibility is there, but only if the other NOC code was also selected in the draw. You need to make the change and include an explanation for the same along with the proof.
For further information, you can write to OINP at
ontarionominee@ontario.ca and get a genuine response.