Tire Sidewall problems of the 1998 Ford F-350

We sold a customer some 35-13. 50-20 mickey thompson atz tires back in 2007 customer brought back the tires in may of 2010 for cracking around the sidewall and lugs contacted mickey thompson about this problem and that received a rga but was not told where to send them called repeatedly but with no answer. This same tire was recalled in 2006 for having the exact same problem was told that the customer would have to pay to ship them back to mickey and if they were in fact defective they would issue a prorated warranty on them if not we would have to pay to ship them back also I do have photos of the cracking all four tire are doing the exact same thing.