Is it possible to really clone a SIM card?

[chronos]

Does anyone know how you might be able to clone a SIM card so that it's an exact duplicate of the original?

I am an AT&T wireless subscriber that got "sold" to Cingular. Cingular is now trying to "encourage me" to switch to a cingular plan by refusing to provide me with new phones, technical support, or the unlocking code to my existing phone until I switch. They tell me that I will have to switch over when my phone or SIM dies. I am fighting this as hard as I can since I have the $99 unlimited usage GSM charter member plan that AT&T sold for a little while. Considering I use about 4,000 mins a month this is huge for me.

I can protect against my phone dying due to unlocked phones but I have no way now to protect against my SIM going bad or being lost.

Any help with this would be appreciated.