iPhone Activation with used SIM?

[Gryfon19]

Is there anyway to force the iPhone to use a current SIM card with my account and the phone number tied to it? I have a calling and data plan on my AT&T account already, but it's at a good price because I receive a corporate discount which obviously doesn't apply to the iPhone. I've read here and there about using an existing SIM with an iPhone but haven't seen anything concrete. Any ideas? Thanks!

 

[fj2007cruiser]

I don't think you can do it with an old SIM.
You activate with their provided SIM
and you may use the provided SIM with another ATT phone, b'cause I did.