If i was to purchase an S8 on AT&T, after the contract is up AT&T will unlock the phone.

However, will the Samsung S8 that was originally purchased from AT&T have all the available LTE bands and work on CDMA ? I don't think it will, will it? i tried using an unlocked AT&T Note 4, once on an VZ MVNO sim and it wouldn't accept the sim, even after getting a successful unlock message from AT&T.

I know iPhones are different and do work. But Samsung S8's do they have one size fits all for all carriers after the unlock ?