Text messaging issues with newly bought iphone 4s

[perezs13]

I I just bought my new iPhone 4s yesterday, and when I send a text to only certain people, they don't receive it, and I don't receive any of theirs either. It seems to be with people who don't have an iPhone. it says the text was sent, and I tried a picture message too and still didn't work. Anyone know how to fix this? Thanks

 

[Munchkinsdad]

If you go to settings-> messages...is "send as SMS" set to on?

I'm not confused...really!