Misselling - contract renewed

I've cancelled my contract on 28/4/2015, agent sold me airtime p.m. but didn't inform me that the contract is going to be renewed for 24 months. My son wants to open a new contract at Vodacom and want to do a SIM Swap with this number where the contact has been renewed but can't do because he has to wait for the 24 months to expire. I've been calling Vodacom cancellations since Monday, 26 November - they promised me that somebody will call me back but up till now I haven't received any feedback. The number of the contract that has been renewed is ***. I don't understand - why would Vodacom continue with a 24 month contract for R71 if they can enter a new contract for R450??