Failure to terminate contract

I have asked to terminate my cell phone contract on the 02/06/2015 and was told it would take 5 working days to complete this task and to port my number over to prepaid, that would have been 18/06/2015. It is now 23/06/2015 and I have not been contacted yet. I have also been loaded with airtime even after terminating my contract on the 10th of June and now will probably be billed for said unwanted airtime etc. This is unacceptable service from a huge telecommunications company such as MTN! I tried several times this morning and even now to contact the call centre 808 number and have been cut off each and every time. How am I to find out the progress of my request when I cannot even get through to anyone?! The cell phone number related to this query is *** and the reference number ***.