Should be a simple question that someone here will hopefully be able to answer.

I have a Sprint carrier-locked iPhone 6s. I purchased the phone from Swappa about a year ago and have been using it on Sprint with no issues. However, we have left Sprint and ported our numbers to Project Fi - all except this number, because the phone is locked.

My Sprint account has never been past due. The phone is paid for and was never financed to begin with. I've used it for a year on the Sprint network and a prior owner of the phone probably did so as well. Swappa guarantees it's a clean ESN and it obviously was for me to activate it a year ago. Yet Sprint refuses to unlock the phone. My two choices are (a) buy an unlocked phone and sell this one on Swappa or (b) - maybe - get a third party to unlock the phone. I see ads for this on the Internet but don't know if they're legit.

Thoughts? Is there any way to get this done?

I've learned two lessons here: (1) I'm never buying another carrier-locked phone again. The CTIA agreement that carriers would provide unlocks when a customer had met basic conditions obviously does not have any real teeth and (2) I'm never going back to Sprint again unless T-Mobile can successfully kill them off for good. (Then I'd still consider T-Mobile, although they still have some hurdles to get over before they can swallow Sprint.)