No Answer - Need to cancel contract upgrade

I have been trying since 8.30am this morning, it is now 11.30am, to try and get through to the 10213 call centre to cancel a contract upgrade on my mobile number, which I accepted on Friday 4/12. I have phoned 4 times and held on for anywhere between 10 - 40 minutes at a time with no answer. No one else can help me cancel the contract. It is my right as a consumer to cancel during the cooling off period, but how am I supposed to cancel if no one answers the phone to apparently the ONLY contact point that can help me? I have tried an online agent on the Telkom website but they informed me there is no other channel of contact. I won't be paying my bill, maybe that way I will get some contact from you. Staff your call centre appropriately Telkom!