Failure to accept liability!

I went to an AutoZone South Africa branch on Saturday 17 March to get a new radiator cap for my Astra H 1.6 GTC the sales guy sold, opened and fitted the cap for me. On the drive home about 12km from the branch my car smelt funny and as I slowed down i was driving 120kmph on open road, my temp light came on and my engine shut down, as I have no heat gauge in my car, the temp light comes on only once it has overheated. when I opened the bonnet it was steaming hot and there was no water in my bottle. My engine seized! (I DO HAVE WITNESSES)

The salesman drove from his branch to my home in langebaan which is 30min away to bring me the correct cap (A high pressure cap) which he purchased from goldwagen with his own money as autozone doesn't stock the correct part. He came and apologised profusely, admitted that he was at fault, knew what the outcome may be and fitted the correct cap but it was too late, he said I should call his manager. The branch I am referring to is Vredenburg, they have been very helpful, I was now under the impression that their head office would be paying for the overhaul of my engine, We all were.

Last monday I received a mail, which makes it now a month without my car... from AutoZone head office saying that my engine seizing was not a result of the incorrect cap, it was me that drove it to destruction.

They have told me that they are not liable and the fixing of my car will be to my account however they feel for me and are willing to supply the mechanic the parts needed, at cost price. My car is currently in pieces on a workshop floor which they initiated with a mechanic suggested by them.

I have since gathered reports that prove that an incorrect radiator cap for this specific engine will result in the engine seizing.

I have correspondence, my original cap and am still waiting for them to drop of the cap that started all of this.

I honestly wanted this to be solved in a civil manner but unfortunately you leave me no other options.