This used to be my #1 complaint about my RAZR. However, after ICS I no longer have this issue. Whatever radio improvements they did with the upgrade made a huge difference for me.
The 4 g would go fron blue to white then disconnect 20 to 30 times a day.after 10 calls to tech support, tier two service, 3 trouble shooting tickets, 3 new phones, sim cards nothing worked. Then I found an app it is called: restore connectivity settings- mororola droid razr.
I installed the app it fixed the issue. I can't believe tech support didn't know about this.