[Verizon Galaxy Note 4 General] DrPhant0m:
Regarding the use of another carrier's devices on Verizon... I tried this. It did not go that well. I was surprised to see a mod post this suggestion, because Verizon's being a CDMA network really limits possibilities. I was then not as surprised to see the ATT/T-mobile reference. When it was said that "most people are doing it" I had to laugh and smirk to myself and think "yeah, right... name someone that has done that on a Verizon account"

Anyway... here's my story:

I did all the research on what 2G/3G/LTE bands were used by what devices... as well as research into "enabling" these bands via Qualcomm development software. These are two very different topics to discuss. I ended up buying a Note 4 that was branded for US Cellular. USC has identical CDMA usage, except for the fact that they do not have LTE band 13 enabled. Only band 4, which is Verizon's "XLTE" band... so that's good at least. US Cellular and Sprint are the only carriers that sold Note 4s with CDMA bands enabled, and USC's come closer to Verizon's. Both are bootloader-unlocked.

To put it briefly... I got the Note 4, which was sold as being "unlocked for use on any CDMA network" and took it to Verizon when my SIM card was not recognized. The phone was still carrier-locked, so I had to take it 90mi away to a USC store, who told me that the phone was blacklisted because $800+ was owed on the account. The end to that story is that I got my money back, and now my 19mo son has a Note 4 to play on. (I now have a Note 4 DE) Also... US Cellular told me that their method of unlocking the Note 4 had been suspended, and they'd have to do it manually, which is less likely to work. They're not OBLIGATED in any way to provide this service on a Note 4. It came out before the mandates of carriers to allow SIM-unlocking.

While I was at the Verizon store... they told me that they did not recognize the IMEI, so they couldn't technically add the phone to my account. It would show up as "Non-Verizon Device" like the Google Play Nexus 6s did at first. Not a big problem, unless you wanted to make changes on your account. Anyway... they filled out some kind of form to "acquire" the IMEI from the carrier. This paperwork never yielded any results, possibly because of the blacklist on the phone from the carrier. This is a separate problem from the phone being carrier-unlocked.

The difference: If the phone was carrier-unlocked, my SIM would have been recognized, and I could have made phone calls and used data... in spite of Verizon not knowing what device I was using. Acquiring the IMEI would not have helped me get the SIM card recognized... but if the phone had been successfully unlocked, acquiring the IMEI would make it show up as a Note 4 on my account.

Side-story...

The reason why I was surprised to see that a mod had suggested to find another carrier's device to use in a Verizon thread is that they should know that this is not a simple task. You can use a T-Mo or "International" edition of the Note 4 on AT&T's GSM service. It's not as simple with CDMA service. There is a largely-theoretical approach to "enabling" bands on modern Qualcomm-powered devices via Qualcomm development software (similar to how Odin is Samsung dev software)... but it seems that each thread eventually gets shut down for clandestine reasons. Not to mention the fact that it seems everyone in the threads are using phones I've never heard of... on international carriers. When I reached out to people that were in-the-know, I got very little information, other than their advice that it probably wouldn't work to turn on CDMA bands on an otherwise non-CDMA phone (like T-Mo or International Edition). They said my best bet would be Sprint, because it's already CDMA (Maybe they were unaware of little ol' US Cellular)... but I probably still wouldn't get the most out of the cellular performance... and the fact that the Note 4 came out before the legislation making phones more "carrier-agnostic" makes it not so easy to get Sprint to unlock it for use on other carriers. When I could cut off 7 fingers, and still be able to count all the CDMA carriers in the US on 1 hand... and they all work on different bands... I don't know what use a SIM unlocking plan is for Sprint anyway. (Though iPhones have all bands enabled on every device... so you could take a Sprint phone to T-Mo... but who cares about iPhones?)

In the "Team US Cellular" forums (like xda for US Cellular devices only, since they don't get a lot of coverage here)... a lot of the community was interested to see how it'd turn out for me, but they were skeptical because they had heard of Verizon's "white list" of IMEIs. The consensus was that I'd be able to make phone calls and get 3G data (both CDMA activities)... but that my 4G/LTE performance would suffer because of the lack of band 13 support on the USC device. When I mentioned the ability to "enable" these bands using the Qualcomm software... they hadn't heard about it, and doubted it was really possible.

Unfortunately... the carrier lock/blacklist on the phone prevented me from ever really trying it. When I got my DE for only $500 last week (yep... heh heh heh), I gave up on the "other carrier" thing.

If anyone here has a friend that has a Sprint or US Cellular Note 4, and their account is in good standing, ask if they will get their devices carrier-unlocked for you to use, and then PM me. Maybe we can see if it's possible. The first thing is to make sure that it's truly carrier-unlocked. Don't take a chance and lose like I did. (Well, I wouldn't call a free wifi-only Note 4 a loss... but you know what I mean)