Supersonic very unreliable

I have been a year with supersonic. I switched from Metrofibre to supersonic on the Metrofibre network as I got a better deal. Trust me you never get the speed stated neither do you get the backup support. My line has been especially poor the last week and I have to go to my phones cellular connection to type this. Promises to come and assess but nothing. Also every time they do the so called background test everything is fine. But not once on Speedtest have I got the correct speed. I always get a story why it is like that. Seriously considering terminating and even paying more but going somewhere else.