Hi all!

Called them again and this time I spoke to a nice bloke named Nick. He said that there were no problems re-booking the ticket and all i needed to do was to pay the fare difference. All well and seems I was very unlucky with the previous CSR whom confidently said that it was against SAS policy to rebook a trip I already started and even if I escalated it, I would reach the same outcome.

Regarding infant seat, it was possible to add to. Altough they did not honor the initial price offer, they said they could add the seat if I agreed on paying 4x the inital price. Not that I had a choice, but I accepted.

Thank you for your help and wisdom!