Caller: Asian call centre

Unless my geeky grandson gave my number to Seagate about a broken hard drive this is one of a bunch of numbers that has been calling a couple of times every hour over the last few days without leaving a message: 0488 805 781 - 0488 859 020 - 0488 858 475 - 048885501 - 0488 855 013 - 0488 859 600. Usually they hang up within four rings but a couple of times it has gone to a call desk and I heard something muttered like ... Jar-He-Kwa ... with others talking in the background. Now how do you block numbers on a flip phone?

they called and I didn't answer as didn't recognise number - then called me back immediateley - tried to ring back on land line - said all circuits are busy now ring back later