It worked
and yes the 2nd change requires a phone call
A lengthy one especially after being cut off from the Indian call centre once

The agent quoted initially exorbitant change fees and fare difference despite choosing dates I knew had cheap fares

On pressing the agent she said she would ask of she was l
allowed to quote the cheaper fares

This was agreed which left the change fee and service charge which is not insubstantial!

Anyway Iceland is back on for 2025!