9 months and still no resolution

I turned in my old Iphone 10 in September 2022 for a IPhone 14 and was supposed to get a $400 credit.  Every month I am forced to call the support number to get the $16.67 credit  ($16.67 x 24 mos = $400) because the phone turned in was never applied correctly to my account.  I just spent 43 minutes on the phone this month while the person read 9 months worth of notes and told me "THEY" would be able to resolve the issue. HaHaHaHaHa…. except its not funny…. and they were not able to resolve it.  I've tried the cancellation department twice in the past and was ASSURED the problem was solved.  NOT!!  Does anyone know of anyone who works at Sprint/TMobile that can override the robot that in the middle of the night "denies" the request for the credit to be applied to my account each month automatically without me having to call in each month?  I would forever be greatful!