Toyota Yaris 2014, gas fuel flap would not open!

[Drum]

Hello everyone. I went to get gas at a gas station yesterday, pulled up the lever by the driver's seat, but it would not pull up all the way, and the flap would not open. So I left without refueling. I am in Canada, and it got pretty cold yesterday, -9C (or 16F), so I had a feeling something was frozen there. The last time I had refueled, I was in the US, and it was raining, the temperature was above freezing. Anyone has an idea how to release the flap if the lever does not work? I do not want to force the lever up as I feel something will break if more pressure is applied. Is there a way to access the actuator or the fuel release cable from the trunk?