Who called from 2489873960

Just received a call from this number - call display showed 248-987-3960. Sounded like he was calling from far away. Asked for the Comptroller of our company. Said his name was Nick from Western Union Business Solutions.  I transferred the call into voicemail (easily to delete that way). Total spam call.

Caller has been calling our office since February 2014. Hangs up after 1 second in vmail. How can we stop these calls from coming in.