Payment plans question

Hello, I was looking to upgrade my iPhone to one of the new ones coming out (the one I have is fully paid off, and I'm eligible for an upgrade). I've always paid in full but was considering going with one of the payment plans this time. What I wasn't clear on -- does going with one of the payment plans affect my service plan? I don't want to change that at all, but the descriptions of the payment options were not clear (to me) on that front. Thank you.