Denial of responsibility if there is no gas - Devon Gas centre

I bought gas on the 6 April 2025 2 14kg gas, when it was time to use it I found out it was empty. The cause of was gas leaked out somewhere, still sealed. Since the cannister was still sealed, I took it back to them they denied that the seal was theirs because it was a "clear one" which they claim they never used. That is the position they stuck to - in effect denying responsibility and accountability. What irked me was the flat denial that I bought the gas there and also making a **** of me saying I did not buy it there. The guy at the store's name given was Aadiel (refused to give surname).