Cell C Poor Quality Fiber Internet is frustrating & discouraging lately

I have called Cell C Fibre support more than five times complaining about poor quality internet or network that start working OK in the morning and end-up deteriorating by afternoon showing one bar and buffering extremely. I have had my Router reset more than 10 times now by the support team to no resolute. I am sick and tired of calling complaining about the same thing and I don't even know what to say. I don't even know if its Fiber Supplier (Metro Fiber) or Network Provider (Cell C) who has a problem, but I believe its Cell C responsibility to get to the bottom of whats causing their network to perform so poorly recently. If I really had more reliable network, I would have jumped ship. I pay a lot of money every month for best uninterrupted network to only receive poor service and I am really tired and disappointed. I didn't even receive reference number