Hi all - I wonder if anyone has a view on the following:

I have a P booking GRU-ZRH / ZRH-GRU, where the second flight was just cancelled and I was rebooked to a new flight which doesn't work for my schedule anymore. At this point, I'd like to reschedule the whole trip, anticipating by a few days also the first flight to ZRH, which is scheduled normally. Problem is, there is no more P availability on that flight as it is in a few days, despite Experflyer map showing lots of space (<20% occupancy). Is it worth insisting to be rebooked also on the flight to ZRH without fare difference, despite that flight not being cancelled (but only the flight back being cancelled)? Tks!