This is the third weird call I have received in the last few days - each from a different number and area code.  I answer and no one is there -- after a couple of minutes the call is disconnected.  I called one number back and got a message "you have reached a number that is disconnected or no longer in service'" and they(?) had just called.

I got the same call from 520-369-3970 and 702-749-5965, but if you listen carefully the disconnected message is not the phone company mesasage. It is fake. But why are they doing this? weird.

This number called last night and did not leave a message on the machine.  In checking my on-line call record, I found that they actually called 3 times within a single minute.  Either they were letting the calls ring for longer periods waiting for an answer (I have a high ring count on my machine), or they were trying to get a rollover to the phone company run voice mail while my machine's message was playing (ring count on that is set even higher.)
In any case... another number for my blocked list.