Most gas stations have removed those warning stickers because it just isn't true. Getting in and out of your car however might still be true.

I have been reading and hearing about this myth for many years now. I remember reading it on the internet in 1999. They said that an Indonesian burnt himself while fueling up and using his phone at the same time. But contrary to popular culture, I believe this myth is just what it is, a myth. No reports about the Indonesian incident were released to confirm that it actually happened. Also an article about the subject was published on the net, which said that both the Cellular Telecommunications Industry Association (CTIA) and the American Petroleum Institute issued statements denying the risks. I�m sure they will not release a statement that may have a potentially life threatening impact on people without much research. Some would insist that phone batteries cause static that will lead to an explosion. If your concern is about the static electricity of your phone triggering an explosion, you have a bigger problem with your car. Come on, our car batteries have more electrical output than your phones. Some run on 12 volts while others run on 24 volts. Thus, our cars have a higher risk of static discharge than our cell phones.