Ring the number and it says the number you dialed is not in service and they never leave a vm.
Calls about about 7 times a day block!!

They call about 3 times a day for the last few days. I called the number back and an automated voice says, "The number you have dialled is not in service. Please try again. Goodbye." Then hangs up. This is another tactic by call centers to get people to pick up their calls by showing a phone number instead of No Caller ID. However, the number they displayed is not a valid number to call back on. Just block them.

Yes. Same with me. Called me several times over the past few days. Calls were not restricted to any part of the day. As per the prior blogger, does not leave a message. I'm based in Sydney...so I'm not sure if this is a state based or national caller

Caller: Unknown number and caller

Likewise, rings 2-3 times a day but never leaves a voicemail. Not worth my time if we aren't worth leaving a msg to begin with.
Don't bother ringing back. Just block it