I purchased a belt sander from the store in Los Ba...

I purchased a belt sander from the store in Los Barrios on a Thursday. the sander was faulty so I returned it the following Monday. They refused to exchange it and they refused to refund me insisting it should be sent for repair. I believe the sander had been repackaged as there was an open plastic bag in the box. I feel I have been stitched up big time and have put in an official complaint but in the man time cannot get on with the jobs I wanted to do.