I contacted the online agent and asked them about changing some flights. The agent put me on hold and contacted EK who apparently told the agent something like 'we can't find the fare' or 'fare rules' or something. The advice from the agent (possibly also from EK) was to fly the first sector on the itinerary (which is not EK) and then phone to make the changes. I asked the agent to email me the specific fare rules but haven't received them, possibly because they can't find them!