Right, so when you sign up for service with carrier A, but somehow finagle it so that your phone spends the majority of time roaming on carrier B's network, you end up costing carrier A extra money (to cover your roaming costs).
From reading HowardForums over the years, carriers seem pretty firm about this. Your usage is costing them significantly more than other users that just occasionally roam, so they're dropping you.
By loading Verizon's PRL (preferred roaming list <of towers>) onto your Sprint phone, it kind of sounds like you went out of your way to help create the situation that you're in.
We you trying to engineer a situation where you pay Sprint's lower rates (and get unlimited data), but trick your phone to stay connected to Verizon's (subjectively "better") network? Best of both worlds?!
Anyhow, sounds like you should probably just sell your Sprint iPhone and sign up for proper Verizon service.
Very well said.
Better port your number now.
Agreed. Best to just do it now and be done with Sprint.