extremely Frustrated - unstable Fibre Network

So I have been with Afrihost for about 4 to 5 years now. December 2018, I have decided to upgrade from an ADSL line to Fibre as the infrastructure within my area has been completed and everyone recommended to go fibre. I am basically just using the internet for phone streaming, updating of software etc. (currently using a 20mbps down and 5mbps up) nothing major, so within February 2019, I decided to get myself a tv box for live streaming and canceled my DSTV subscription. With everything set up and excited, I started realizing how slow my network is, music videos on YouTube buffering constantly or just taking ages to load, so I do what any normal person will do, I switch of my router, wait 10min and switch it back on, upon doing so everything seems to be back to normal but, after a few min. we’re back on the buffering. A week ago I mailed Afrihost support, requesting them to please reset my port on their side to enable me to eliminate the fibre line as fault, on which I received a shocking response from the support center, stating that they cannot rest the port and recommend that I reset my router at which this wall take my router to factory settings, which means I would have to get my IT technician at a fee to set everything back up again. So no help from them, and alternatively starting to blame my supplier for the tv box and that it’s faulty, I did a more intense test yesterday which includes taking a speed test every 20min or so, before during and after attempting to stream something, to my shock, I established that it is indeed my fibre line being incredibly unstable. The infrastructure within the complex is Vumatel, and my neighbor on the same infrastructure experienced no issues during the time of my tests, although he is using another ISP. The first speed test I did indicated between 17 and 19mbps download, which is normal for a 20mbps line, but a few minutes later it suddenly drops down to between 2 and 4mbps download, then few minutes later its now back up to 16mbps and suddenly it drops again to as low as 0.45mbps. So I decided to make contact with Afrihost support again, informing them about the unstable line and to please provide me with a solution, and this morning I received once again a mail from Afrihost only now stating that they have checked my account and I do not have any active packages, yet I have been an existing customer for 4 to 5 years, been billed each month which is paid up to date and I receive internet (if that is what you call it). So, my question to Afrihost, is this just incompetency, what are you going to do about this to resolve my issue and should I get myself another ISP?