Save some cost at the pump law

This law would stop gas stations from changing the price tell after they get the new gas in there tanks

I have talked to many gas station mangers and friends who own gas stations about this very subject. Every morning they get the a phone call from the gas companies that tell them what the gas is going for that day. However they have already paid for the gas that they have in there tanks why do they get to charge more for something that is already paid for. I was at a gas station a year ago and it was in the morning and they decided to up the price as I was pumping my gas they made me come back in and pay the difference they stated that this was the law and that I must pay the rest of the cost of the gas after pumping Something needs to be done for us whom depend on gas to get around please help us at least see only one gas price per day or per time that station gets more gas its like they are double charging or something at least that is the way it feels please lawmakers take a look at the gas station laws and see if something can be done to make sure the public does not have to pay double