Thank you so much for the information.
If I give up South America and change from AONE4 to AONE 3, I know there is no refund, but the current rate of AONE3 is more expensive than original AONE4, do I have to pay the diffrence or just change it with no refund?
I would call the airline that issued the ticket. I believe you may get the taxes you paid on the segments you bypassed refunded. Other than that you should just have to pay the $150 reissue fee for the reroute not the price of a new ticket. I am NOT an expert.