I have recently purchased a pack of space saving(vacuum) bags through ebay. On trying to use the bags I find that 50% of them do not retain the vacuum. On ebay I do not find any provision of lodging a complaint. The only provision that is available is to leave a negative feedback. And before you do that there is a provision to contact the seller. I have done that, but I am not receiving a reply from the seller. What do I do?