Inoperative NBN

Level 2
Hi all, I have tried for over 10 months to have our NBN repaired as it cuts out for hours and sometimes days at a time. No it’s complet dead. The tech teams keep checking and find the line is dead and they request an NBN tech and nothing ever happens. Been told twice in the last two weeks NBN techs would be in contact but when the NBN cuts back in it auto cancels the techs then hours later the NBN is dead again. This has been an ongoing problem and there has been no solution even after NBN techs came out mouths ago. Not sure what to do now as we have 3 in our house at uni. When it is operating the speeds are very very slow. Im on a NBN 50 plan but we only get an average of 10.5 Mbps download and 8.2 Mbps upload. What should we do next as it’s now impossible to even get anyone at TPG on the phone or tech chat line?