I would complain to Toyota about them. Let us know how you resolve it. I'm having similar issues since I got new tires. In my case, it could be alignment and not the tires, although I didn't notice the wandering with my old tires. My car is due for service in a couple of weeks, and I will talk to the dealer about the problem and have them check the alignment.
When I had a problem with a dealer that literally tried to swindle me on service (long before my Priuses), Toyota told me they don't control their dealers and that they're all independent businesses. Basically, "pound sand because we don't want to hear about it."
