Mizco International, Inc Mizco - Digipower Defective camera battery. They won't return messages. Mailed battery and they have moved with no forwarding address. Internet

I purchased an LP-E5 battery for my Canon camera from Best Buy in May 2010.  I did not open it until I needed to charge it 7/27/10.  The battery would not slip into the battery compartment of my camera.  Best Buy told me that since it had been over 30 days since I purchased it, I would have to call the manufacturer.  On the back of the package is the phone number and email address of mizco/digipower.  I have sent an email once a week and called them at least once a week leaving polite messages and asking for a return call.  No one has returned my phone calls or emails.  I then went to their website and followed the return instructions on their "Warranty Policy" page. I mailed the battery to their Customer Service at Brooklyn NY.  I paid to mail it priority with a signature confirmation request which I could track online.  The package was returned to me stating that they had moved with no forwarding address.  I have continued to call and email Mizco with no results.  I will take this up with Best Buy in Ft. Smith, AR this week.