Payment Support Fee?

Just upgraded my phone to the Samsung S25 Ultra.   I did it through the App as they had a special to avoid the $30 activation fee in store. 

First bill shows a "Payment Support Fee" for $10. 

This was never displayed ahead of time. And no idea what is means.    I am calling TMobile again as they did this last month when we updated my son's iphone with some weird fee the store never told us about...and the CSR could not explain the fee but gave me credit.

Also reporting this to the Consumer Service in myState.... seems Tmobile tries to sneak in these charges.