got a call no message no idea who this is

This phone number calls me all the time so I added it to my phone's blacklist. However, they have left me messages twice, and each time the message is just background noise or silence.

Transworld systems (likely debt colection )

I didn't answer it because I heard something about phone calls from a random number. Really strange that the location of the call is from my hometown, it almost made me pick up but I decided to google it first :P