Disappointed customer

Spargs Sutherland fuel on 26 Sutherland street Mthatha are selling **** gas, on the 28/06/2025 I bought a 9 kg gas cylinder, got home and used it for my heater, and on the 4/07/2025 this gas is finished, mind I only use it for my heater, which I get home and switch on then later switch it off and go to bed as you know you can’t sleep with a gas heater on so as a result I only use this heater when I return from work and in the morning when I prepare for work. This gas has lasted me exactly 6 days how possible is that if a 9kg was filled ? The store unfortunately had no F’a to give told me that’s my problem not theirs… normally a 9kg cylinder with last me at least 2 months as I live alone and in the only person using this heater.