It's someone using a coded number for their aynonmous intentions. It's not a bot but a person who does not want to call from unknown but a number people can see but when they call it back; they can't reach the person that called. 9/10 times people rather answer a number they can see rather then just unknown written in their caller id.
972-591-7440 - Just called our business. Illegal robocall trying to offer business loans. Reporting the call to the FCC.gov website as harassment, as the calls keep coming in over and over throughout the day, and the illegal call offers NO Opt-Out option.