Change of tickets and venue

Nataniel show 23 October 2015 20:00 - booked and bought tickets 6months ago. Booked seats right in front. The venue was changed and when we got here they told us sit where you want. This means paying and booking to sit in front had no meaning and ended up sitting in the back. I want a refund as this is unacceptable. Why not cancel the show than making it such a inconvenience and price mess up. Paying to sit in front and getting a back seat. Please do something about it!!!