Paying off iPhone early

You can pay early. See How to view and pay Apple Card Monthly Installments - Apple Support

including the following:

If you want to pay extra on your Apple Card Monthly Installments, you can Pay Early. Before you can Pay Early, you need to pay your entire Apple Card balance.

If you are buying using the new Monthly Installments, you will have an Apple Card account. You are signed up for that when you choose to pay via Apple Monthly Installments. You can pay the remaining balance using your bank account as described in my previous reply. If it is an Apple Card Monthly Installments and you want to pay online, you can do that through https://card.apple.com/

If you are using Barclaycard (another financing method for Apple products) you will have a Barclaycard. I strongly suspect that you can pay early on that also but I don't know that for a fact.

Yes you can. And I don't believe Apple still uses a different bank for the Apple Upgrade Program assuming you don't want to buy one with an Apple Card.

Thanks deggie. I wasn't referring to the Apple Upgrade program. I was referring to buying an Apple device online or in store with financing. As of last week at least I was offered 2 options for financing -- Apple Card Installments (a relatively new option) and also the older Barclaycard option.

If you had expressed an interest in the Upgrade program you would have been given a third option. You can also pay off that one early.