Stop robocalls

I missed 3 calls from this number within 1 minute. No voice mail of any kind was left. When I attempted to call the number back, A computer sounding voiceover stated: "this is not an authorised number" followed by loud digital tones before it disconnected. I only found out that it was the Junee Correctional Centre after I actually answered the call when the exact number was attempting to call me again. For some reason the telephone number is not anywhere close to the Junee area code. If