Go to the USPS website, go to contact USPS, ask a question about a package, input the tracking number and all the information requested. This will go to the local branch of delivery and they can track it down from there, they usually call so be sure to answer the phone, it takes anywhere from a day to several days. If you have the keys to your PO Box, you can cancel your order via your USPS account. For those without keys, call the USPS Customer Care Center (1-800-222-1811) within 30 days of the original payment date. If you are well within 30 days, you can also email tech support for a refund request.
Here is how to speak to a real person when calling USPS customer service.
Dial 1-800-ASK-USPS (1-800-275-8777)
It will ask for your zip. Dial your zip code. (or speak it)
It will ask about privacy policy. Dial 2. (or say NO)
It will ask about customer survey. Dial 2. (or say NO)
It wlil start listing menu options. Dial 1. (or say PACKAGE)
It will start listing submenu options. Dial 1. (or say TRACKING)
It will ask about letters in the tracking number. Dial 2. (or say NO)
It will ask you to say the tracking number. Ignore it and say CUSTOMER SERVICE.
You should finally get connected to a customer representative or be given the choice to continue waiting in line or be called back when your turn is ready. Only the last step above requires actual voice input. The voice recognition software that USPS uses is awful so dial your answer whenever you can.
So I've been trying to get a status update for a package that's 2 days late.... After hours on jumping through hoops in the USPS phone system, I stumbled upon this:
Dial the USPS 800 number (1-800-275-8777), when the woman's recording comes up, press '0' nine time (one after another, without pauses), after a short pause, you should be in-line to speak to a live person. It worked for me, hope it'll work for you too.