Vodacom fibre *****s my money

For almost a year I have complaining to Vodacom fibre about my service. I pay for a 100 Meg line and my complaints fall on deaf ears. Every time I complain they say on their side they see I'm getting 100 megs. Yet when I do tests I never get more than 60 Megs. They say on their side it's fine so there is nothing they can do. I want you to come to my house and fix the problem. I have now used their speed test and for 3 tests haven't got more than 50 Megs. Now they say they'll look into it. I want this sorted out. How can you take my money and not supply a service.