Switching from Virgin Mobile and CDMA

I've been researching online, and have come up with the following questions. Is it possible to:

A) Switch from Virgin Mobile's prepaid, CDMA (non SIM Card/GSM) service and hardware, to a new prepaid account with a major service provider under GSM, such as T-Mobile?

B) Purchase an unlocked phone and SIM Card for the new account?

C) Keep the same number from the old Virgin Mobile account to the new account?

Thanks