Unlocked Sprint S6 on Verizon?

I have an unlocked Sprint Samsung S6 and I'm trying to get it to work on Verizon but it doesn't want to work. It shows an exclamation and R where the signal bars are. I have tried setting up the APN and a Verizon rep put the sprint phone in their system, but that didn't work either. Is there any way to get this to work? Do u have to flash Verizon's Rom to it? I noticed that even unlocked it still seems to have the sprint activation stuff..... Please help, scoured the Internet and forums to no avail :/