Laptop never arrived! Still got invoice 5 months later?

Last October, I ordered a Precision 5680 and it never came. The people who bought me the workstation filed a chargeback because it NEVER ARRIVED and I eventually bought a Lenovo Thinkpad, which did come. Despite this, almost 5 months later I'm sent AN INVOICE in the mail by PAYPAL for this  Dell <Profanity is not allowed. DELL-Admin> laptop that NEVER CAME. Get your act together or help me by explaining what happened.