Brand New iPhone 3G On Family Talk

[cheezy]

Okay, I want to know if what I am saying is correct, if not correct me.

I want to buy an iPhone 3G and be on my Fiances family plan which is her parents and herself. If I'm not mistaken it is $10 to add somebody to your family plan, and it is $30 for the data plan, so would I be paying $40 a month. Or would I just have to pay the $10 for being on there plan?

Also, I know it cost to activate/unlock your phone through AT&T. Could I Jailbreak my iPhone and unlock it, then take it to AT&T and get my plan set up? or would they not do it because they didn't unlock it?

Thanks In Advance

[bhz1]

$40 I have a family plan with 2 Iphone 3G's (othe rphones as well) but its the cost of adding the line $10 PLUS teh data plan $30.