The person creating the upgrade plans should get fired

Short but direct... 

Dear customer, please give me back your old phone and get the new one for free. 

You do that and they give you credit back for your more expensive phone you had over 2 years. 

1 year goes by and you want to upgrade with the new promotions or the Jump program.

The issue? You loose your credits for the remaining 12 months.

To make things worse, I can buy the brand new Flip 4 for $800 from the Samsung page right now and keep my Flip 3... or…

Pay $500 now to own my Flip 3, get $400 off the Flip 4 and pay $1,100.

It is cheaper to buy the new phone for $800 and keep the Flip 3 vs upgrading with T-mobile for $1,100!!!

Whoever designs those upgrade programs should get fired unless T-mobile does not want you to upgrade and packages those upgrades to sound nice and people who don't run the numbers will pay more in the end.