2002 Kia Optima Gas tank

For the last 2mos. I have not been able to put gas in the car without it clicking off every few seconds. I have tried different stations. I called the dealer and they said it would cost $95.00 to diagnose it! Seems to me that there must be a vent to let the air out of the tank when putting gas in? If so where is it and how hard is it to get to.I am retired and don't have a lot of cash to throw around.
Thanks so much