Seems you only can cut your loss here and take the refund. SV will or can do nothing since the booking has been cancelled by your OTA. I assume any new itinerary is a higher fare? I hence usually book directly with the carrier unless price differences are significant, but even if you book with SV directly issues happen - there is a whole thread on an involuntary downgrade to Y for TUN-JED in March-April where getting a rerouting via SV was for many an ordeal.