Harrassment by agent

I received a call from a very rude Agent, I have no idea where they got my number. I declined to talk to him, he called repeatedly, harassing me about why I hung the phone up on him. In my view, where someone cold calls you, without an instruction from myself to ask them to contact me regarding service, it should be up to me to decide whether or not I want to speak to the said agent. I am very disgruntled at the fact that they somehow got my cellphone number and harassed me.