I'm in the same boat as you are. I am an Alltel customer but where I live I roam on Verizon. Now, I'm not sure if your aware of cell companies roaming agreements (google is your friend
). But this is the issue you and I and probably many many more people are up against. Alltel has EVDO roaming agreements with Sprint but only 1x roaming agreements with Verizon. So, if the network your roaming on is Verizon thats all your going to get for now. Your phone will default to the strongest signal which seems to be Verizon in your case. Also, one way to find out which tower your using (Verizon or Sprint) dial #611. If your on Verizon it will tell you.
After several calls to Alltel and a little research I found out that in January I wont have to worry about this. Because Verizon's buyout of Alltel will be completed. I will then have EVDO Ra in my area.
I hope this helps you..