I have received several calls from this number but never annswer (or return the missed calls) because it has no caller ID other than the number and they never leave a message.  I just assumed it was some type of scam and am not interested in verifying it.  

How can these calls be be stopped, anybody know?

Caller tried to get me to provide personal information in order to receive $200 upgrade on my phone from Sprint.  When asked if they could send the information in the mail for me to review I was told it was a phone promotion only.

I did not answer the incoming call on my cell phone (I am a Sprint customer, also), because I didn't recognize the number.  However, I did call the number back from my desk at work, and a woman with an Indian accent answered the phone saying, "Customer Service, how can I help you?" and told me that she was offering a free upgrade on my phone.  I told her that I wasn't interested, and that she should remove my number from their call list.  She said that she would have them remove the number from the list.  I'll give it a couple of days, and see if the calls stop.  I'll post an update to report whether or not the request worked.

I received the same call just now.  I was leary, but did at least give them my name to see where that would get me.  Aferwards she kept pushing to get me to purchase a new phone that moment and they would give me a $200 rebate.  I kept asking if I could call Sprint's 800 # and get the same offer and she said no.  She also had an Indian accent.  I think they are a total scam.  glad I didn't fall for it!

i'm glad you didn't fall for it either.  I never thought about googling an unknown number...i'll have to remember that.