problem with AT&T sim card

[Bossman]

AT&T prepaids do not roam outside Canada and Mexico. So, that's why it's not working there in Italy. You should be fine when you get to the US. I am not sure how long the initial activation lasts without topping it up, if it's 30 days or 90 days. Regardless, you should be able to top it up online if needed.

Originally Posted by dan1988

I'm in Italy now, I bought the sim on ebay and I activated it yesterday on the AT&T website but the sim card doesn't work.
The sim card was brand new (i had to detach it from that card - i'm sorry, i don't know how call it) and, after the registration, the website gave me my phone number.
I need the sim on December, when I will go to the US.
Do you think that it will work once I will be there?

Thank you.