Bobshop does not protect the bidder

I have spent a fair amount on BobShop mainly because I found it a distraction bidding online and the fun of sometimes winning the bid at a reasonable rate. I have just been cheated for the third time. How it happens is that you will bid on an item, which shows the stock level, and wait patiently for the deadline and pay your due. However, for the third time the seller has come up with an excuse 'out of stock' and then they offer you a refund. I maintain that if the seller is not willing to sometimes make less profit, they should not make it available for auction. bobshop customer service just go through the motions with half excuses and lame apologies with no regard for future loss of business. Really disappointing.