I can understand your frustration. Ive been having issues with peak time speeds for week now. Im on vivid 152 (150mbs about) between 4pm and 12am i only get about 0.30 on average.
Ive tried phoning, my dad tried phoning. Each time we were just told messed around with. One support guy said "check your superhub lights" then hung up, another told me about maintinence and then another gave me false information that didnt work. A phone number and website.
My dads on about phoning for a reduction on the bill if it happens again today. Since were only getting half a day on our internet.
Never had issues for years till now. I even made a topic asking for help and trying to figure out why but it never got a response. :/