What can we do about the oil companies ripping off the public when the government is on the companies side?

I know it will be an uphill battle, the government won't help and i know people need to use gas for there lives but it doesn't mean there's nothing we can do, perhaps something like discovering and boycotting only the biggest rip off company till it is so financially hurt that it stops ripping people off and then boycott the next biggest rip off company etc. till they all behave themselves and they all fall in line simplely from it being more profitable to do so.