calling early in the morning

Sardar: What is the name of your car? Lady: I forgot the name, but is starts with 'T'. Sardar: Oh, what a strange car, starts with Tea. All cars that I know start with petrol.

He said I he represented a school collection agency and I have never had a school loan. He said he needed to verify my address. He left this in a voicemail and ended the call by stating that if I did not call back I would have further charges pressed, which is not a legit claim because one has to accept in person by their signature or send a letter of acceptance/denial of any accusations before accepting to go to court unless subpoenaed by actual court officials

no message left called about 3 pm

Whenever I get a call from this caller no one is there when I pick up the phone. Then when I call the number back I get the recording service that says "this number is no longer in service." What do we do to keep them from calling and why are these people being allowed to do something so pointless?