Supersonic finance team is unreachable

I got signed up for a 2nd fibre service which I didn't consent to, and as a result I got double billing for 12 months or so. I've asked for an updated statement which doesn't have the second service fees, and their finance team is quiet on the matter. They are unreachable via calls and they never respond to mail. They're quiet, yet I do not have Internet access through their service. Their call centre lines disconnect when trying to get hold of someone from the billing department, mind you this is after they put you on hold for a very long time. Boom, you're asked to rate the service yet you are waiting to be connected to billing team.