Dynasty Gas - do not use them to buy gas,. leaking bottles

So i purchased a 19 KG bottle of gas and a 9kg. The 19 KG was standing in my lounge and I just smelt gas. I broke the seal and connected it to my gas stove. used a match to test it and the whole thing went up in flames. I disconnected the bottle and took it outside immediately called the company. They wanted to come into my house and test my stove because according to them it was my regulator - i told them i was not comfortable. Asked them if i could bring the bottle the saturday but i had a family medical emergency and whatsapped them asking if they could come and fetch it instead. they only read and responded on 2 May. I was waiting for them and sent them a message yesterday I wanted a refund and the 16kg exchanged for my original empty 19 kg and my money back, now i am the one that is in the wrong - they refuse to refund me my full amount- they will only refund me for the gas left in the bottle. it is not my fault that the bottle is leaking.