I am having the same issue. It was confusing when originally I got the device in Oct of 2017. I got an iPhone 8 Plus which I have been paying so called "FlexLease" for over 36 months now. Which when I called customer service to get it resolved they originally said they will adjust the amount of about $400 I paid extra. After two weeks I see no updates and when I gave them a call back, they say there is nothing in their notes about $400.
I even asked if they could at least let me just own the device after paying so much extra. Never had an issue like this since I have been a customer, which is almost 10 years.
The so called "Customer Service" keeps putting me on hold now and then eventually call just disconnects. It's just frustrating the way they are treating me.
@Sprint_Khoury any way you could help me with this?