Verizon and Sprint are compatible it would have worked.
I didn't say it wouldn't. But OP did not specify his devices and not all devices have the same frequencies.
And once the phones were paid off Sprint could have unlocked them so their they could be used on Sprint.
Easier said then done. If OP paid them off first then ported, sure. But the other way around? Sprint is being very difficult lately. Their reasoning for denying unlocks to people who port out now is that they are no longer customers and can't help them.
There was a law passed a few years ago that allows you to get your phone unlocked way easier now
Ah yes, this is a common misconception.
Yes. President Obama signed a law. No. It doesn't make it easier. For you or any other customer anyway.
Do the carriers have to unlock? Yes. But what the the customer commonly fails to understand is that the law allows the carriers to define the policys in which they will unlock. If you do not meet a single specific, point they can deny you the unlock.
They can deny you the unlock by saying your device was manufactured before February 15, 2015. They can deny you an unlock by saying it would be extremely difficult for them to unlock your device because it was technologically designed NOT to be unlocked. A prime example? The Sprint iPhone 5. Sprint won't unlock it. But they'll give you an MSL code. Which does nothing for an iPhone.
In short, the 'law' has holes in it large enough to deny you your unlock in any way you can imagine and plenty more the carrier can dream up.
Lastly, there was also an agreement that the carriers came to around the time this 'law' was passed. Most of them are abiding by that. But that isn't a law and sometimes people confuse the agreement the carriers have with the law.
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Interesting. HSPA is itself based on CDMA so it seems like there's a bit of both mixed in there
Yep, which is why I said, deriavtive of. I just recently, myself learned this. So, LTE, while derived from GSM also has some CDMA components.