Robo call.  Will not accept return call.

Found this number in my call logs.
Name              Number               When                   Length
Unavailable     512-692-7633     TUE, 07-07-15     0:32

512 is my area code, but the number is probably spoofed.
Search engine results say
"Its exchange 692 is managed by XO TEXAS, INC.. The number is currently on switch number AUSTTXGKDS0."

Found this number in my call logs again.
The caller left no message on my voice mail.
Name              Number               When                   Length
Unavailable     512-692-7633     Thu, 07-16-15     0:32

Found number in my call log
Name         Number                  When                              Length
UNK           5126927633        1 Sep 2015 5:23PM CST  0.39

I am on Fed and TX DNC list but makes no difference.

This is how it went:
512#: Hello is this ____?
Me: Hi, what company is this?
512#: Don't worry we are not selling anything...(Thick hispanic accent)
Me: Ok, what company are you from?
512#: <click> call ended.

It's amazing how easily you can get rid of these people by just asking basic questions such as, "who are you?"
You DON'T have to give out ANY info over the phone, not even confirmation of who you are. That's not anyone's business but your own.