With the new sim that they give you, can you put it in an AT&T phone? will it work?
Yes, you can put it in an AT&T phone and it will work. BUT, first you must activate the SIM in the ST Nokia phone for which you ordered the SIM card. Once activated, the SIM card carries all the ST information necessary to use the ST service.
People usually lose the Nokia E71 phone with the SIM card in it unless they have already transferred the SIM card to a different phone. Getting a replacement SIM card without the phone runs the risk of deactivation and loss of deposited funds. One will already lose funds when the phone is reported lost.