MWEB worst ISP!

I have been having issues with MWEB since I joined them. They keep saying there is nothing wrong with my Fiber line but my international speeds are only 5mbps on a 100mbps fiber line. ALL MWEB can say its not their responsibility as an ISP for anything outside of SA. Wow really then who should fix my issue? Apparently MWEB is not an ISP but and NISP - No internet service provider!