I purchased an (supposedly) unlocked Verizon Note 8 online. My Boost Mobile rep said the phone should work with the service. It has not connected to the network at all. The ESN comes up as allowed to bring the phone over. This process has been a big headache. Yes, I too get that message about sim not being Verzion but no calls are going in or out. What do I have to do to get the two to work together? I think the rep did not have the latest codes to put in the phone to work with Boost.
Hi Tashema! Here's what's at the root of your issue...There are basically 4 main carriers in the US: Verizon, T-Mobile, AT&T, and Sprint. Verizon and Sprint are CDMA networks while T-Mobile and AT&T are GSM networks (Google it for more details).
The nice thing about Verizon issued Galaxy 4G LTE phones is that they are also GSM unlocked. This means you can insert a SIM card from T-Mobile or AT&T and use your Galaxy on their networks. Yes, when you power them up there will be a notification that your SIM is not from Verizon, but you can just swipe the notification away and it won't show up again until you restart your phone.
You cannot, however, use a Verizon issued phone on a Sprint network. They are both CDMA networks, but their phones/networks are incompatible. So here's the problem you encountered: Boost Mobile (and a gillion other resellers like them) is what's called a mobile virtual network operator (MVNO). MVNO's resell one or more of the major carriers networks. And Boost Mobile happens to be a Sprint reseller (in fact, they're actually owned by Sprint), which means even though your Galaxy is GSM unlocked, it will not work with them (see notes above).
If you want to see what I'm talking about, check out this list of MVNO's:
https://en.wikipedia.org/wiki/List_of_United_States_mobile_virtual_network_operators
So the key to using your unlocked Galaxy 4G LTE phone from Verizon is making sure that the service you're signing up with is either a Verizon, T-Mobile, or AT&T reseller. And almost all of these companies have an online IMEI check where you can see if your phone is compatible with them ahead of time.
Hope this helps someone!