I've been an Animas user for the past three years, and I'm not surprised at all to hear that they haven't registered your returned pump yet, but I am surprised that they haven't responded to your phone calls. In my experience, the package tracking and return receipt process usually takes about two weeks to register at Animas, meaning at least one or two pre-recorded "reminder" calls to send my old pump back to them. But when I call customer support, they can always find it immediately and are incredibly nice and apologetic for the overzealous calls/delayed system. Due to a recent issue with my insurance, I had to speak with the billing department and even they were wonderful and responsive.
I've only called after hours with tech support issues, so I suppose my recommendation is to call during business hours when you can be sure to talk to someone. They have access to the tracking number on the prepaid UPS label for your pump, so they should be able to track it through UPS and inside their company. Again, it's on the inside that the system has always slowed down for me.
Can you check the UPS tracking number to make sure that the package was actually delivered? One thing that may have slowed down the works is if you dropped the package in a UPS air box because the label only buys you ground service. This may have caused some delay on the shipping side, so checking with UPS could clear that up as well.
Good luck! I hope you're enjoying the ping, he's my favorite.