Q: cellular data network

What do you mean, "if it does not have the option"? Do you have "Cellular Data" turned ON in Settings > General > Network?

If you don't see "4G", "3G", 2G", "EDGE", or any of that sort up in the top left of your iPhone, then you are not in range of a cellular data network.

Cellular Data must be on. That's all you need, unless the phone has been hacked or jailbroken.

Ah, you are asking how to select the network. The answer is your phone is locked to one network, so you don't get a choice.

Oh. Yes, as Lawrence said, your phone is currently locked to the carrier it is on now. You need to call them to inquire about getting it unlocked for use on other carriers.

You need to ask AT&T that question.

Authorized Unlock an AT&T iPhone

StraightTalk uses the AT&T network, and people have reported that a phone locked to AT&T will still work with StraightTalk.

I dont have cellular datanetwork too..what should i do??

I contacted ST. Here's the instructions they gave me.

1. using wifi, open safari

2.go to the address iapnupdatetf.straighttalk.com

3.install the profile

4. make sure Cellular Data is on

5. turn off wifi and give it a try

hope it helps

How do you install the profile?

If you go to that address using Safari on the phone it should install automatically.