Loyal customer not supported from vodacom

Very angry and annoyed at vodacom. I have been a customer for over 11 years and get treated like my business don't matter. I've installed a fibre line with 200 up and down load speed but get around 4 mps - 200mps or cut off saying no internet. I've logged 4 calls with 14 follow up calls but the calls get closed with no resolution. I pay every month for a service I'm not receiving. When asked to cancel they want me to be liable for costs which is really unfair as they aren't providing me with the service