can i pay off the lease earlier

See the following: What’s the best way to buy an iPhone? - Apple Support

Reasons to pay over time

• You pay in installments, often with 0% interest and no money down.
• You can choose a payment plan that works for you.
• There are many plans that let you upgrade to a new iPhone every year.

I was going to do the same thing when I purchased my XR, but I don't recall off-hand how to arrange that. For specifics Contact Apple Support

With either Apple’s regular product finance offers (through Barclay Bank), or the iPhone upgrade program (through Citizens One bank), these are 0% consumer loans (0% if paid fully within the terms limits).

iPhone Upgrade Program Terms and Conditions

https://www.apple.com/shop/browse/financing

Since these are 0% consumer loans, neither bank is going to blink twice if you want to give them their money back early. But you’d need to contact the respective bank about doing that as Apple does not manage your loan (since it’s not from them - Apple got paid in full when you got your phone).

Was your phone financed through the Upgrade Program?

Call and make arrangements with Citizens One.

That is a question you would have to ask to the supplier and credit provider.