Have a reservation USA-Japan (3 segments, 2 connections) under one PNR for two people made with lifemiles. One person is not flying anymore, so I want to split the PNR from one to two passengers separately and then cancel one passenger. I would also like to change flights (dates and carrier and maybe connecting airports but not origin and destination) for the second passenger. I understand the change fee is 150 USD and the cancellation fee is 200 USD. Will avianca change me two fees or one (change) fee for removing one passenger and modifying flights of the other one? Or should I just cancel the whole 2-person ticket for one cancellation fee and rebook from scratch? Will still have to pay the new booking fee of 25 usd.

(Originally had to book two seats and options were limited but now for one person better flights are possible)