Elite Upgrade Issue

I'm having an issue on one of my lines on my Mobile Account to do an Elite Upgrade on a Premium Unlimited line. Every time I add the device (checking "upgrade existing line" and the necessary information for Elite Upgrade) to the checkout cart the monthly credit disappears and it seems an early upgrade fee of $70 is being randomly added to the total but not in the breakdown. I have tried with other devices and same issue. My other line I have had no issues upgrading on Premium Unlimited. I even went into an Xfinity store and same issue came up without an employee who could help get around this issue. Multiple times I have been on Customer Support Chat and have received no help on the matter. Please advise how this can be resolved. Thank you.