I FITTED new GT Radial tyres to my Smart Roadster. I chose them because of cost, quality, warranty and the service I received at the front desk. In no time at all I noticed the handling was crappy and the tyres were set to 42psi instead of the recommended 29psi. To what degree is a business answerable when it does not deliver a basic service such as safety?
THEY have a basic responsibility to deliver a professional service, and it seems they haven't. You should complain to the company so they can take action to make sure it doesnt happen again. If that doesn't satisfy you, find out if they're a member of a trade organisation and make your concerns known to that body. You could also report your problem to the manufacturer/distributor of GT Radial tyres so they can take action. Finally, go to your state consumer affairs people and lodge a complaint.