Unlocking Samsung s7 for at&t to use with sprint?

I can buy a brand new s7 for cheap but not sure if it will work with sprint I know you can call at&t to unlock it but he still owes money on it or should I say has 2 years left on the contract. Hes old and doesn’t like the phone so he offered it to me. He just uses his old phone because it simpler. At&t wont unlock because of this. Sprint said if its unlocked they will give me a different sim card for it and I can use it. How do I go about this, is there a problem because he still under contract with that phone?Any help would be great before I buy it.

Whoever you are getting the phone will have to do the unlock process with AT&T but the phone itself is capable of working on Sprint from the specs on Samsung’s site.

If he owes money on it you, another carrier probably won’t activate it.

I have used services online (ebay) who can unlock phones in like 1 hour.

They give you the codes and instructions to put into the phone.

I have unlocked some brand new samsung galaxy gophones to work on another carrier, but this issue with the contract may be a problem.

Might be worth investing 2 bucks or whatever the unlock shop charges for the codes.