Henceforth, alternate to this option after the online process for a seat upgrade; there is another alteration for Upgrade Flight Seats in IcelandAir. You can dial the official phone number, which you can retrieve from the contact us phone section; once you dial the number, select language preference and press the option to communicate with an assistant for the upgrade. If there is seat availability for the newly chosen class, then you will have to pay accordingly from the direct guidance of the assistant.