If the dealership balanced them twice without resolving the issue then they should still be looking for the source of the problem. Have you told the dealership they haven't fixed the problem? If so, what did they say? if not, that's your next step.
I wouldn't let the dealership off the hook yet, there's plenty they can do other than just a basic spin balance, i.e., PicoScope with NVH kit, Road Force Balance, rotate tires, replace tires, etc., etc.
JMHO
No expertise implied or expressed