Err no. If you didn't order something and a company sends it to you, the FTC says it's yours. If the OP really didn't order a phone from Sprint, then according to this post:
FTC's Site
It's his to keep. "Karma" has nothing to do with it. Legally he isn't obligated to return it unless he actually ordered it. It gets awfully frustrating reading about people's subservience to companies on this site. First installing software on your phone voids your warranty, now you've got to go out of your way to give Sprint back a product you aren't legally responsible to return to them? ROFL. If you make a mistake and ship Sprint something you weren't supposed to, good luck getting it back. If they do, somehow they have a right to charge you? I. Don't. Think. So... and neither does the FTC.