Unwanted contract upgrade

I have a contract with MTN where I received two sim cards with R50 airtime each month for R50 per month. The contract was taken 2013. In March this year, I received a phone call from The Mobiles Plus Team, telling me about the exciting upgrade. I was told that I will get a new Nokia 503 for R89 plus free (rescuebox, safetybox, phonebox,tech trace). I agreed on the deal. The new phone was delivered. I checked the confirmation email a week later. On the email the total cost was R290.I called back and told them that this not what was agreed on. Fortunately I did not open the new handset. I was advice to take to any MTN oulet. I went to MTN Standerton and they told that that there franchise they and can not help. I went to Secunda Mall MTN, same story. Final I went to MTN Secunda Shop no:22 Pick & Pay Centre. I left the phone there on 24 March 2015. The phone has been there since then. I also pass there yesterday, 15 July 2015, it is still there.<br> I have sent emails for clarifications and on how to cancel the contract completely, but I have not received any satisfactory reply.I also decided to cancel the stop order from my bank.<br>