MTN & Call Centres & Cooling off period & Consumer Act Contravention

One of MTN's call centres (Empowered) called yesterday to move my contract from a month-to-month onto a new 2 month contract. They confirmed that there is a 7 day cooling off period. Today, 1 day later, I have been trying to cancel the upgrade and move back to the month-to-month, due to details of the contract changing. To do this, I have to call 135, but then get told that MTN cannot cancel this, and the call centre has to do it. However, all numbers that MTN has for the call centre do not exist - it is impossible to contact them.

My contract is with MTN, and thus all contractial obligations are those of MTN. MTN should be dealing with their call centre, and not expect me to do so. I have no contract with the call centre.

Please assist me ASAP to get this resolved. At this point, MTN is in contravention of the basics of the Consumer Act, as it's impossible to enforce the cooling off period.