Is it possible to disable roaming entirely, not just networking during roaming? When trying to google the solution to this I mostly just find instructions on how to disable data connections during roaming.

To clarify why I'm asking, I have a contract with a small local phone company and they have a roaming contract with a large local provider. When roaming on the large providers network I get calls at the same rate, but no 3G network. My phone seems to quite frequently choose to go roaming even in areas where the home network gets full strength signal.

Is it possible to stop an android phone from connecting to roaming networks?
Just go to flight mode or remove the SIM card when you are on roaming.