866-575-8296

They left a message on my voicemail saying that I needed to call them because they needed to inform me about changes to my monthly billing account. I do not even have a credit card with them.

Same caller and same message: Ineeded to call them because they needed to inform me about changes to my monthly billing account.
I do not have an account with Best Buy.

Same thing happened to me... I called the actual Best Buy number and got no answers... thanks Best Buy!

The call is about a warranty/service plan that you purchased, most likely a phone, and the card it was deducting funds from has expired

I received the same thing, but I did call them.  After refusing to "update" my credit card information (which they would not have even had, since I have never had a "mobile phone warranty plan" through Best Buy), I pressed "2" to speak to a representative.  After some very awkward and suspicious recordings telling me I was next in line (clearly trying to sound legitimate), "Sean" came on the line and wanted my name and card information in order to look up my plan.  I told Sean where to stick it.

itis probably in reference to your black tie sevice  example  cell ohone