2004 Jaguar S-Type Tires wearing inside

I bought 2 new tires "Perelli's" at a chain (Tires Plus), in addition I asked them if they could do a front end allignment, after about 3 months or 5,000 miles Imy front tires were wearing, I went back and they said the alignment was fine but did another one, I went back 3 times since because the wear had gotten so bad that it was pulling the car. This time I told them to swithch the back tire to the front and if the old tires do not show wear on the inside then it must something wrong with the tires I purchased. They said anything was possible. Well it has been 2 months and another 3000 miles on the old tire in the front. To my supprise there is no wearing on the inside to be found. Any advice would be appreciated. If the car is in total allignment what else could make the tires wear uneven or "towing".