The monthly savings should pay for the phone in less than a year!
So... let me see if I've got this straight. You're effectively paying the exact
same amount for the next year that you were
already paying, only
now you had to buy another refurbished phone at $300+ (assuming the "less than" a year payback when you consider taxes and regulatory fees) to replace a likely already perfectly usable handset that probably could have lasted for at least another year or longer itself if you took care of it, go through the headache of data and network migration, and get no promise of being able to keep that new price after your year with Sprint at the current price point just so you can wind up being on the precarious and past headache inducing absorbed network end of a T-Mobile merger complete with unpredictable price changes after that point, all with a phone that you bought that outside of the Galaxy S8 or iPhone 7 models they're currently selling possibly won't even work with T-Mobile's network
after the merger outside of the Sprint footprint until that spectrum gets refarmed, or let you carrier unlock to go back to AT&T with until at least 18 months from now?
*squints*
Are you sure this is as good a deal as you think this is?
It's not too late to back out, friend...