Aquí tienes un mensaje claro, firme y en inglés, con toda la información que quieres expresar:

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Hello,

The last tracking update for my package shows “Delivery Completed – Illinois, USA.” However, it has been stuck with the same update for more than 8 days, and my order was supposed to arrive before this week, which clearly did not happen.

I want to highlight that I do not live in Illinois.
My correct delivery address is in New Jersey, and that is where the package should have been delivered.

I urgently need clarification regarding:
• The exact location where the package was supposedly delivered
• The name of the person who received it
• The carrier responsible for the delivery in the United States
• An immediate solution since this delay is unacceptable

Please investigate this issue as soon as possible.

Thank you.
Daniela Orozco