I am trying to book OTP-AMS-SEA-SLC operated by KL, DL, DL, with an overnight in AMS. All connections less than 24 hours. Each leg is available as an award: the KLM flight is available on DL website and the DL flights are available on FB and VS websites (AMS-SEA and SEA-SLC individually are available on FB and VS, but not AMS-SEA-SLC when searching for AMS-SLC).

How to book this over the phone and have it priced origin to destination instead of as a sum in miles of the three individual segments?

Are FB agents able to long sell?