gas filler clicks off before the tank is full

Any codes?Sounds like you could have a vent valve issue or a spider built a nest pinched hose etc.

Thank you. Regarding the Code,I went the local Autozone and got P0452 (Fuel tank pressure sensor condition)with the following explanations:1)The evaporative emission system sealed condition is monitored by this sensor Probable Cause(s): Fuel Tank Pressure sensor defective; Check connector and wiring; check hoses and fittings
My question is: Is the Fuel tank pressure sensor a part of the Fuel tank and whether it can be replaced by itself or I have to replace the Fuel tank?

That code will not cause the gas pump to turn off early.The code you have is for the fuel tank pressure sensor reading .1 volts or less back to the computer.You would need a scan tool that can read live data that will show you what the fuel tank pressure reading is.With the fuel cap off it should read about 1.5 volts.If it doesn't you could have have wire problen or sensor issue most likely causes.The sensor is on top of the gas tank and should be replacable by itself.I have seen animals chew the wires up.

I have had the same thing happen to me it is most likely the purge cannister is dirty it can be cleaned and will work fine the purge vents the fuel tank so when you are filling up the pressure has no where to go so the pump shuts off the same principal as when you pour a fluid out air needs to replace the void if the purge is plugged there is no where but the filler neck for the pressure to go and in turn shutting off the pump