Terrible customer service and slow to no internet

Terrible customer service and even worse internet speeds. The only way to reach them is via Facebook Messenger. We have fixed LTE as there is no infrastructure for fibre in our area. We have NEVER had issues and we have been with Supersonic for 3 years. Suddenly we have constant bad connectivity or none at all. Streaming is impossible and one can’t even watch a short ad without it buffering constantly. The answer I got is that fixed LTE is best effort - clearly more like NO effort. Why after ALL this time is there suddenly an issue? Crossing fingers it gets resolved soon or I am cancelling my years long subscription and going elsewhere (which I have also heard is an issue!)