I will never have Sprint based solely on my experience w/ their customer service and policies regarding locking phones, even when they are specifically designed by the MFR to be open to any carrier.
I bought a Samsung S7 from a guy who had it on Sprint, even though he paid off the phone and cancelled his account, when he sold it to me they refused to unlock it so I could use it on Verizon. I called no less than 4 times and every time it was damn near impossible to get somebody to even talk to me (as a non-customer) and when I did, every time their explanation was different. 2 people said it was cleared and unlocked, others said nope but not my problem. Finally I was forced to go a different route and have a 3rd party unlock it.
What I learned in the process is that none of their reps know anything about how the IMEI system actually works, nor do they care to. None of the local stores do anything the least bit technical. Basically if you need to do something the least bit tech savvy YOYO.