MWEB not taking accountability for poor service!

I opted to upgrade my fibre line with Mweb from a 50 Mbps line to a 1 Gbps line. In doing so, I had to purchase a new router of R699. I was on the new plan for about a month and a half. In that time, I observed I was still getting the same speeds as my previous plan (between 30 - 50 Mbps) and the speed rarely went over 50 Mbps. At one stage I contacted Technical Support to troubleshoot the issue and it was quite clear that I was getting well below the advertised 1 Gbps over LAN cable and up to 800 Mbps over 5 GHz wifi. This lead me to eventually downgrade back to the 50 Mbps speed and go back to using my previous router. Upon asking Mweb to credit me back the difference between the two plans due to not receiving the speeds advertised, I was given a straight NO by one of the managers in the Accounts department, as there was no fault lodge for the issue. I'm failing to understand how I can get on screenshare with a technical agent and clearly show the speeds are not what I'm paying for and yet they refuse to adjust my billing due to no fault getting lodged. If I was getting slow speed on only a single device I could understand but the same speed for half a dozen devices clearly shows the issue is not the client devices. On top of that, I'm now stuck with an unused router which I paid R699 for.