I just paid my Next Up balance on two iPhone 14PMs, not the full amount.I'm sure if anyone else is having this issue. I'm on Next Up and I tried to make the required payments to be able to upgrade but it's asking me to pay off the full amount of the phone. I spoke with ATT and they said they're not able to take those payments until it's time to upgrade. I've never had any issues in years past so I just wanted to share just in case anyone is on Next Up and is having issues.
I used the "manage wireless" link then "Manage Installment Plan"