Failure to honour guarantee

I bought four Firestone Destination A/T tyres for my car, the purchase of which was accompanied by a guarantee TRG230998. One of the tyres badly blew and I have therefore requested that it be replaced. This was several weeks ago and I still dont have a replacement. I am therefore driving without a spare tyre. I do a lot of driving, and at least once a week this is quite late at night on the dark N1 between Johannesburg and Sasolburg. I am extremely concerned that I dont have a spare, as I feel this potentially creates an enormous safety risk. I have been advised that the tyre is on order, and that stock is waiting at Customs. However, this does not help me right now. Given the concerns I have around my personal safety, I would like Firestone to either commit to an immediate replacement, or at very least two new tyres for the back wheels.