Sprint customer getting strange calls

I just received a call from that phone number as well.  I generally don't answer calls unless there is a name via Caller id with it, or I am expecting a call (like from a doctors office with numerous phone numbers), otherwise, I let it go to voicemail then determine if I am going to call back or not.

This call did only had number listed on the caller id, and did not leave a voicemail.

My guess, a spam call