Telkom Breach of contract

Telkom trotted my UNCAPPED internet down to 20kb/s. when I contacted them they told me that I only have 150GB on my UNCAPPED contract and that after the 150GB they will throtel it down to 4MB/s.

this is unacceptable. I cant even open a whatsapp on my phone with 20kb/s. if telkom does not fix this I will stop paying, I don't care about the contract because in my opinion this is a breach in contract on their side, I can live with 4Mb/s, but 20kb/s?!!! NO!

And what really makes me angry is that they refused to help me.