Half filled cylinders by Afrox

I bought a 9kg cylinder that had gas in it. It lasted less than 7 days. I used this for my gas heater. I had anticipated that it would last at least three weeks. There was no gas leakage observed yet the gas got finished so quickly. I also did not switch in the heater 24hours of the 5 days I had used it for. So I decide to exchange the gas for a full one at a garage. My brother checked whether it was full but it wasn't full. This is not okay most especially because I am struggling financially because of COVID and I need to have a warm place during this COVID times. I sure hope there is no foul play here. Otherwise, it begs to be looked into because this does not seem normal to me as a consumer.