Tyre external force

My wife bought two tyres a couple of weeks back at Dunlop lakeside in Germiston on a friday and Saturday morning, hardly 24 hours later, as she was driving she had a tyre burst. The trye was torn right round on the side. We inspected the tyre to check for any punctures or anything that could have damaged the tyre. We sent the tyre back to lakeside and they sent it to Jet park technical services. They sent the tyre back and claim it's not a factory fault and it got damaged due to an external force. We got in contact with the guy who check the tyre and with an arrogant and condescending tone told us he checked it and it's not a factory fault. I tried to ask him to explain what the external fault could be but was just irritable and said something about under pressure and an external force. He said there nothing he can do for us. I even explained that I'm not disputing he's findings but we need clarity and to understand how a brand new tyre get damaged like that. I am very unhappy with this service and still feel confused as to how that tyre got damaged. I am very unhappy with the overall service of Dunlop