If you are doing the switch at an ATT store they will move all of your contacts from you BB to your iPhone for you. They did this for me when I made the switch. If you are doing it yourself I'm not really sure, the only way that I know how to do that is to move your contacts to your sim card then import them into the iPhone, but I am not sure that this can be done when coming from a VZW Berry.
If you are doing the switch at an ATT store they will move all of your contacts from you BB to your iPhone for you. They did this for me when I made the switch. If you are doing it yourself I'm not really sure, the only way that I know how to do that is to move your contacts to your sim card then import them into the iPhone, but I am not sure that this can be done when coming from a VZW Berry.