I have done some test here and noted that something else might connected to your network as well so can you provide below detail to me.
Make sure cable coming from wall socket is directly connected to gray DSL port of router. I suspect technician might haven't completed job because DSL should be stable, normally it will take 3-5 minutes to come up once we connect modem, I believe you have tP link Vr1600v VDSL modem router.
See below link for set up,
Is there MDF/communication room in your building?
can you try other socket?
was service proved by nbn technician with his modem/ your modem during visit?
otherwise probably MDF jumpering require here.