I feel ******

I purchased the 9kg gas from builders Warehouse. On the 11 June and on 16 June the gas was empty. I normally last me 3 to 4 week's. I use for heater only and I normally use 1 bar. I went back to builders Warehouse they said am not the only person who complained. And there is nothing they can do because Afrox will always say it went through quality check. I feel ******