Terrible internet connection

We took out a 50mb data contract with vodacom last November and it was working okay for a month. Now it's just garbage. Most of the time we can't even stream, it just loads the whole time. A lot of the time we don't even get 50mb speed when we do a speed test. We thought that leaving our old provider to get better service from Vodacom was a good idea but now I don't think so. We can't keep paying for something we not getting.