Afrox and BP selling an empty tank

On the 15th of May, last month I bought a 9kg gas refill. To my surprise by the 20th of the same month, the gas was used up. It was very much shocking to me that it would deplete in such a very short period of time and yet only used for a gas heater, in which the image is attached on the email. I then went to the BP garage which I had purchased it from: BP, Dorp Street, Stellenbosch, Cape Town. I went there with the intention of letting them know that I will never buy gas from them again as I was anyway under the impression that no one would want to take responsibility for it, so I was not there for a refund or an exchange. However, with the consultation with Management regarding the issue at hand, I was informed to bring the empty tank and proof of purchase so that they can raise the issue with the Supplier, which is Afrox. Indeed, I did as told. A week later, it came to my attention that I need my empty tank as I have no heater and it's very cold in Cape Town. I went back to BP for feedback and to take my tank back. I was informed that the feedback received from Afrox is that nothing can be done as the tank came back empty. As if the empty tank wasn't an issue anyway! I then sent an email to Afrox explaining the above because I am now a bit aggrevated because I live far from Stellenbosch for me to drive there, three times and don't even get an apology but informed that they will not do anything. Afrox then responds and says I must email them the BP's telephone number, which was confusing because how do they contact them upon their weekly delivery! I go ahead and search for the telephone number and email it back. Afrox comes back to say that yes, the manager is aware of my complaint. Afrox then tells me to go back to BP or call them to say that they must call Afrigas so that they come with the resolution, my goodness! Again I call BP and explain the above. A week later, BP (Mariaan) comes back saying they have no resolution and therefore I must call their superior. Mariaan has been the lady handling my case for BP and Buti Rikotso is the manager from Afrox who handled my case. I am very disappointed at both companies. Especially Afrox because two of my close family members work for them!