Upgrading phone through app Issue . Full retail price instead of installment options Phone is paid off and bill is current .

When the iPhone 15 came out I was able to upgrade my phone through the app on installment plants with no issue. The other phone on my account is a 12 Pro Max and has been paid off for close to a year now. I’ve been trying to upgrade it through the app But the only options it is giving me is paying for retail. But if I go in the store or call they able to upgrade me. I want to be able to do it through the app since also sales tax is cheaper when you order it through the app versus the store. It’s almost half the cost . Is anybody else experiencing this issue with ordering it through the app?