Bubble nightmare

I bought an air bubble mattress (anti-bedsore) 4 months ago for my mother who had a stroke. The mattress has a weight capacity of 135kg and my mum weighs about 57kg. The mattress had a 1 year guarantee. After 4 months the mattress started to deflate and I found the hole in one of the seams, and I tried to patch the hole with the patches and glue provided, but was not successful. I contacted Takealot and return the mattress to them. After inspecting the mattress, they said that the mattress was damaged by me (improper use or something like that) and they will not be replacing it. I went onto takealot online, and the specific one that I bought is suddenly not for sale anymore. There are ones on there that look similar, but cheaper. I will not recommend them either. This was not a cheap mattress. Is that how they make their money? Conduct business? Sell inferior products and then blame the customer? I will be taking my business elsewhere.