Cell C Fibre - lack of support

I’m experiencing very slow internet on our Cell C Fibre connection for the last two months. I have logged multiple tickets with the support desk but they have not resolved my issue as yet. I only get a response if I follow up on the ticket, no proactive engagement. The issues starts every day at 18:00 and last to 22:30, my 50Mb line goes down to 1.5Mb download and 0.5Mb upload during these hours. The internet is un-useable during these hours. I’m not sure how to get a response from the C-Fibre team, please don’t use C-Fibre for your home internet. Shocking support