My understanding is that Israel controls borders and the flow of goods and people in both Gaza and the West Bank and block whatever they please. Do Palestinians have exclusive control over any external or internal border? I'm not aware of this and doubt it since this would be dangerously close to granting Palestine an independent state, and Israel is not about to do that.
For what it's worth, the Wikipedia article seems to describe Israel as in control and capable of overruling any Palestinian decision at the crossings. https://en.wikipedia.org/wiki/West_Bank#Crossing_points
I could see it for the crossings into Israel but how would they control the crossings in to Egypt and Jordan.
Their borders are controlled but only on one side by Israel. Why aren't they using the other border for things like mail. Or for everything.