The RL4920 will switch all buy itself after rebooting frequently, to automatic where it can ROAM. It switches from the sprint setting only, for calls to automatic. Check this after you have booted this phone off and on for a while. So far Sprint will not acknowledge this or do anything about it. Instead they stick you with a phone that can ROAM on you.
Sprint PCS phones can be set to only work on Sprint PCS network, therefore a user never has to worry about roaming. Which is one of the reasons why I stayed with Sprint. So, with this phone changing to automatic all by it self, means you could answer a call while roaming and you will be charged.