Other Fuel System Tank Filling/charging problems of the 2018 Chevrolet Traverse

Fuel pump shuts off when filling as if tank was full. Sometimes it happens multiple times during a fill up, sometimes it does not occur. Dealer stated there was gas in the vent line and charcoal canister, and that the tank had to have been overfilled. Dealer ask stated they blew out the lines and canister as a courtesy, and if it happens again, we will be expected to pay to replace the vent line and canister. We have never over filled the fuel tank. After the pump clicks off we stop. If there is fuel in the vent line and canister, there must be a missing/defective part in our fuel system, either allowing fuel in, or delaying fuel cutoff until it is overfilled. I filled up on 4/28/19, the first time after the service, and the pump stopped erroneously 6 times before filling up the final 4. 5 gallons without stopping until full.