Empty gas cannisters sold

I have used the contact form on your website, but after a week have no feedback at all.<br> <br> I have on two separate occasions paid for gas canisters that then turned out to be empty. Since I used them weeks after obtaining them (I have more than 1) I could not take them back to the store, as they'd just tell me I had used them in the time I'd had them.<br> <br> One of them came from the Smit Street Spar in Fairland, the other from the Pick n Pay in Blackheath. I know of other people who have had similar experiences.<br> <br> What can be done about this? Are you missing a QA step in production? How can I get my money back?<br> <br> Keith