NBN Help

Level 2
Hi there
I had a scheduled appointment for the tech to come and install NBN at my house yesterday between 8M and 12 he didn't turn up !
I had to go to the shops and he turned up at 2.30 when I wasn't home and my 13 year old son told him I wasn't home so he left
He has now said that he installed it etc ..I have set the modem up perfectly and still no internet
What the he'll is going on ??
I sat on the online can't for 3 hours yesterday to get no Where

Someone help pls