Please check the following thread where I explained how to refund your ticket. http://www.flyertalk.com/forum/9739511-post14.html

The question is, did you try to refund your ticket before the traveldate or afterwards? Afterwards it is not possible to refund a Spezial-Preis ticket. Before it is possible. So if you tried to refund your ticket before your traveldate Deutsche Bahn should have give you money back minus the 15€ cancellation fee.