EasyJet is not currently charging for rebooking fees due to the uncertainty with COVID-19. You still need to pay the fare difference.
This is in the case where the traveller who has a valid ticket for a scheduled flight would like to change the flight on their own decision (the cost is normally 50€)
I tried to look for an announcement that would set end dates for this campaign but did not find anything. EasyJet's pages just use the word "currently".
Is there an end-date for that zero rebooking fees campaign?