Fuel Delivery problems of the 2005 Chevrolet Avalanche

Filling up with gas on my 2005 chevy Avalanche. While filling with gas, with the lock on the gas despener, and watching to make sure it stops, when the gas despenser stops, about 2-3 seconds later gas starts to spray and/or leak out of the gas tank. At first I thought it was just the gas station that I used, but it has occured at mutiple gas stations. I feel this is a major safety concern that should be looked into. The dealer has said that there is nothing wrong with the vehicle, and nothing they can do.