I thought all Verizon phones came sim unlocked. Am i wrong about that?
You are correct. Verizon's LTE devices have been SIM unlocked since they started releasing LTE devices with the Thunderbolt. Having SIM unlocked devices was a requirement in one of their original agreements to acquire spectrum for LTE from the FCC.
I've used almost every Verizon phone I've owned abroad with various local carriers without issue for many years now. Every now and then I still read stories where people are surprised that a Verizon device is SIM unlocked, but it's been that way with all of them for years now. The real story would be a Verizon LTE phone that's not SIM unlocked.
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This means you should be able to sell yours a bit easier considering you won't have to find a buyer with the same carrier! Good on you Verizon!
People will need to be careful there, particularly if selling to a buyer in the US. Sure it's SIM unlocked, but the issue with Verizon's devices is LTE band support. Verizon's LTE devices often don't support all of the LTE bands that are used by AT&T and T-Mobile. They support some, but not all.
AT&T and T-Mobile use bands 2, 4, 12 and 17 for LTE. Of those bands, the Verizon S7/S7 Edge only supports bands 2 and 4. So while a Verizon S7/S7 Edge will work on AT&T and T-Mobile, it will be falling back on 3G and HSPA+ quite often. A buyer should be made aware that while it will work, it may not work in the same way as a device from their carrier or an unlocked device would.
Verizon also often makes changing the APN a bit of a task, which means it can be a chore to get data working on a non-Verizon network. Early reports are that it's a bit easier with the S7/S7 Edge.