Vodacom FTTH speed not even close to what I am paying for

Since signing up for a 100Mbps uncapped FTTH subscription, I rarely get the download speeds as advertised and what I have signed up (and paying) for. During specific times of the day, download speeds will drop to less than 10Mbps (have myself and wife work from home using that speed is an impossible task). I have logged numerous SR's with Vodacom. They open the SR, but close it after a couple of days without ANY feedback. I have been phoning, emailing, used social media to try and get assistance - NOTHING! I am paying in excess of R2500 per month for my FTTH and cellphone contract, and this is what I need to deal with. I just get no response from Vodacom concerning this matter, but I am promised they are "investigating the issue" but nothing gets done. Vodacom - will you be able to get this issue resolved or not with or without the relevant parties involved, or are you happy with the number of people cancelling your subscriptions (where in my area I know A LOT of cancellations taking place)?