Looking to upgrade an Iberia flight from Premium Economy to Business.

I can book at the lowest price on Iberia (BA have not yet loaded the lowest price premium economy fares)

2 Questions

firstly, can the flight be upgraded using Avios from my BA account (I don't have access to an Iberia account) even if the flight is ticketed by Iberia

secondly, if I can upgrade, do I have to phone the call centre, or can I do this online.

Many thanks