Question About the Apple iPhone Upgrade Program!

My question is this: We are required to go up to 12 months, then we can upgrade to a new phone... at that time we return the current phone we have. If I pay it off before the 12 month period, will I be able to upgrade and keep the phone I have?

I'm thinking about signing up for the Apple iPhone Upgrade Program, but I want to know if I pick up the iPhone 7, will I be able to keep it when I upgrade to the next iPhone if I have paid off the iPhone by then?

Thank you!