I've looked a bit through the threads, but wondering.

I booked on KLM.com (UK site) for Aberdeen to AMS (and beyond) and the site says that I can select my seat when purchasing ticket. There was no prompt, so I bought the ticket and later have gone in to select this route seating and says 'not possible'.

As I have only a 50 minute transfer time in Schiphol, I'd like a front seat. How can I accomplish this?

Thanks