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As I read it, if you do IUP from Apple, you will have to give your Verizon account and hence they charge an upgrade fee.

If you have bought it outright with sim-free model, then you might not have to pay it. It is like BYOD. That is how I read here from people who did not pay the upgrade fee.
Correct if you buy a sim-free model and you insert your own sim card, they can't charge you the fee. Being that Sim-free model iPhone X isn't available during pre-order, you would have to order the Verizon model.
 
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