When Vodacom's service is BAD but they won't take your calls to cancel a contract

Vodacom is the absolute worst!! They increase tariffs during a fixed term contract I've been trying to cancel my contract for the last 3 weeks I've made 10 calls and after 5 to 10 min of waiting the calls are dropped every time. On their chat the consultant was going to get the cancellations dept to call me, still waiting since last Friday I've already made 3 calls thus morning before 8:30 and been disconnected every time, now they gave very high call volumes (since last week, all day long)