Can I finance an iPhone with Apple Card without activating with a specific carrier?

So I’m looking to finance an iPhone with my Apple Card instead of buying it straight up. I have a plan with a phone carrier that isn’t available on Apple. Do I HAVE to activate with one of the four carriers? Can I just cancel right away? Will I have to pay in full when I cancel?

[Re-Titled by Moderator]

Original Title: Financing iPhone