any device upgrades in store must be paid for up-front at the store before receiving the device : (
unfortunately, the only way to get the charge added to your bill was to ship-to-home when ordering (or to order over the phone with a phone rep once they have stock)
i don't know if anything is different for corporate accounts but i don't think it would be
edit: oh, as meowmix said i guess not all of the stores can even access corporate accounts! my bad~
How much data does your plan need to have in order to be able to upgrade to the iPhone x? I'm currently on a family plan with 1GB, but we didn't need to change it when someone on the plan got the 7+ last sept.