I'm useing a iPad 3G SIM in My iPhone 4?

[kmmxracer]

So I got a iPad 3G SIM to work in my iPhone 4 useing this guide
Activating an iPad 3G SIM without an iPad

My question is: is there a way ATT can figgure it out?
And I can send Text messages witch seem strange to me. I'm a bit out of the loop when it comes to the network stuff, so my hope is some of you guys know enough to know if ATT will catch on and flag my phone.

A little bit of info:
-Useing "broadband" as APN(Changed it with unlockit.co.nz)
-Used a IMEI from an old prepaid phone to get to the activation page to start the Data plan.

[Volerikan]

Well, you can send txts, but it will not arrive to the recipeient. AT&T can see it, but it's unlikely, I wouldn't worry about it.

[kmmxracer]

Ya, I meant to edit my post last night. The texts look like they are sending out, but the never get received on the other end. Thanks for the reply