Answered the call and heard noise as if someone was listening but never said anything. I immediately call back and got a message saying,  "This number is not in use. Thank you."  

I want to know the purpose of these types of calls. I have received several calls from similar numbers in the Tampa Bay area with no clue or connection I could make.

Perhaps a private investigator could root it out?

called and it said "this number is not in use. goodbye"

Getting called everyday for the past 3 days, and no one is there and then they hang up...tired of it!!!!

Lots of background voices. Russian accent. "Congratulations. You have been selected for a free $1200.00 wireless security system."

Tell them "idi (e-d) nahui (na-hui)" and the calls will stop.