2006 mercedes benz c230 sport really hard to put gas at the gas station

every time when the car needs gas it will only let maybe 1 gallon or less on
slow fill it shuts off the attendant states the fuel tank is not vent air through the
filler tube it taks over 45 minutes to put 10 gallons in moving the pump handle
around in and out it continues until he fills extremely slow or just and very hard
to get the pump handle out of the filler neck