Spam call centre that's been hassling my phone repeatedly. I didn't stay on the call long enough for their pitch

call centre -- after I answered they clearly hadn't heard my "hello" so were just saying "hello" themselves. I didn't feel like responding and they didn't say anything else (even though they would probably have clearly been able to hear my ceiling fan in the background) and then eventually hung up.

Called three times today most likely a scam as when I answered on the third call no one was there