Mitsubishi Lancer 2006: Front end squeak

Ever since the 3000 km service on our 2006 Mitsubishi Lancer LS we have been telling the dealership about a very annoying squeak coming from the front end, but they could never seem to pinpoint the problem. They kept using the excuse that they could not hear the noise. I finally put my foot down and demanded they fix the problem when it went in for its 45,000 km service recently. They changed the lower control arm bushes, which fixed the problem for a day or two, but it soon started squeaking again. I took it back and this time they found that the left hand shock absorber was shot. The problem is that they only want to change the one shock that's shot, but I think that is ridiculous because one shocker would then be 46,000 km older than the other. We have contacted Mitsubishi, but they don't want to know us. What else can we do?