delivery missing

I ordered a prepaid USIM a few days ago.

It finally arrived but was received by someone I don't know. (I can't understand why the delivery man gave my package to the person) I'm looking for my package desperately and now I'm in despair.

What I want to know is what will happen when I can't find my USIM forever?

Is there any way that I can cancel the order because of the reason that I couldn't receive the USIM actually?

Also, where can I contact to solve this problem? It seems like At&t doesn't provide sufficient help for consumers.