As KLM rebooked you, then it sounds like they have taken over the booking/now own the booking, and it should therefore be possible to use their refund tool (although the ticket was originally booked with a travel agent).

I would suggest trying to fill out their online refund form and see how far you get:

http://www.iscinfotech.com/rps/Forms/frmMain.aspx

(This form is not hosted on the KLM website; if you think I am being devious and misdirecting you away to a third party for nefarious purposes, you can satisfy yourself that this is indeed the site linked to from the KLM website - see their page dealing with compensation and refunds - the link appears there, called "Apply for a refund":

http://www.klm.com/travel/nl_en/plan...nd_refunds.htm