No response from mtn

<p>Good day</p> <p> </p> <p>I upgraded on 23 October 2014 with mtn and January I started paying R750 and now they are telling me that I still owe R18k and my contract will be payed up next year December where as my contract stated 24 months and I have been waiting for the response for the whole month I have sent proof of purchase and everything but no response and I have been calling and visiting mtn stores nothing. and they keep deducting. </p> <p> </p>