Megamaster - Defective gas bottle

I bought a 5kg gas bottle on 9th July 2023.....had it filled at Builders Pinetown
the following week...used it connected to a two plate gas stove for load shedding purposes..the open close know was stiff but could turn on and off but now appears to have seized in open position..continued correspondence with Megamaster since 27th July to date..complaint sent..then photos..then a video..then I must use vice grips..and now I must take the stove and bottle and gas pipe etc to Builders and get them to sort it...it's a new item full of gas .I am a 65 year old woman..unacceptable