AT&T Costumers!??????!!!!?

ok im going get the iphone 4 but i wanna a ask a question about plans ok DataPlus 200 MB,Nation 450 Rollover Minutes,diz whre the question come in @ if i dont add messaging unlimted mobile to mobile will i not be able to text becuz it has this other thing None - $0.20 per Text/Instant Message; $0.30 per Picture/Video Message.