iPhone Hacking Questions from concerned 3G user

Sometimes at busy locations (Malls, etc) I get a phone call from an unknown caller. Have had the phone for 2 years now and seldom have received any calls out of the ordinary. One time, while at the mall, I got a text that said So what do you think about this 1 pretty lady. I was very disturbed by that text.
Dont know what my OS was before but I am on Iphone 3G and just upgraded to 3.1.2 per the Itunes Update Feature.
My settings are: WiFi off, BlueTooth off, SMS/Texting off, I think (I do not text and told ATT to turn off texting due to the Hack Alert I read about recently regarding SMS), Location Services ON, passcode ON, DATA/Internet access ON (I browse frequently only sites I am familiar with like yahoo mail). I use the GPS app frequently as well.
With what I think is SMS off my friends text me but I never receive it although I do receive texts with minutes remaining from AT & T, which is weird.
Also, got a phone call from unknown caller once when someone was driving by my house, could that be a coincidence? These calls typically ring once or twice, then hang up.
Is there a way someone can find your phone and just call you by being in some proximity to where you are or through internet connection?If so, how close do they need to be to do it?What can a hacker access on your phone.Please send references to reputable source reports regarding your answers, like AP reports, Cnet, Apple, CNN, etc.
Thank you for whatever information you provide and happy holidays!
Message was edited by: UniAtomNeu
Iphone 3G iPhone OS 3.1.2