Why is my honda civic 2003 EX overheating?

OK, so I took the car back to the car dealer where I got it and they changed the thermostat, head gasket, new water pump tube. I still see the car over heat and the reserve tank fills up to the top. Should unplug and empty all the coolant and change it with brand new one?
I just bought new reserve to install and will be doing tomorrow morning. Just wondering why it still overheating and my reserve looks full still?

PS: I just picked up the car today from the dealer and they told me if it keeps overheating then the radiator might need to be replaced. I need the car and want to see if it is a more simple fix where it just needs to get cleared from inside.
Added (1). I also replaced the radiator cap before I took it in to the dealer to get things changed so the radiator cap is new.

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