Impossible to change product or cancel

Requested to change product on 21/09/2015, received a reference (***A). Consultant advised that change will be effective in 24hrs. 24hrs later there was no change and called telkom again, another consultant then advised that product change takes up to 72 hours. 3 days later still nothing. Called again and consultants advised that it will only be done by 29/09/2015. Still no change up to current. Received an sms to advise that a technician will be coming on site, after taking off from work to ensure I can accommodate the technician he didn't pitch up. Want to cancel with Telkom but can't get through to the call center. Telkom is definitely the worst company in the world. Please either attend to my request or cancel my service. Otherwise I will withhold payment.