Yes, you can only have one installment plan at a time, but I’m saying the credits apply to the installment. They don’t apply if you want to pay off your phone. If you’re halfway through an installment plan, and you want to pay off your phone, you’d have to pay the remaining balance without the remaining credits. For example, if you have $1000 in credits over 36 months and you pay the phone off in 18 months (having used $500 in credits over the previous 18 months), you give up the remaining $500 in credit that you would have gotten over the next 18 months. If you keep the installment for the full 36 months, you receive all $1000 in credits.