Silent calls

Got a call from this number, but nobody spoke and then the call disconnects after a few minutes.  When you

call back the first thing you hear is "Good bye" then "Please enter the number you wish to call".

Does anybody have any idea on what this latest scam is ??  Also received identical calls as well as the exact

same responses when you return the call from the following numbers:
                  2267829965
                  5146679781
                  2898071653