You can order a device only iPhone 6 on the Verizon website following these steps.
https://forums.macrumors.com/threads/1776008/
good luck with that...attempted when they went on sale, got flagged for fraud the next day, and then 2 days later, they claimed my credit card info was incorrectly entered, and canceled the order (even though my card already had a hold on it). So, you can try, but don't expect it to work.
It did work and it still does work. I ordered an iPhone Thursday that delivered the next day and I ordered again Friday to be delivered tomorrow.
Verizon website flagging your credit card as fraud has nothing to do with the process of placing an order. As you can see on the thread, plenty of people have ordered and received their orders. I'd call your bank or use a different card.