unable to terminate contract

my son's contract cell no ***was due for expiry on the 28th February 2015 . I was told by the consultant to contact cancellation dept on the 27th February 2015. In the interim I went to the MTN store at Mall@ carnival and was not the same thing. I contacted the customer service dept on the 27th February 2015 (with long extended periods of waiting with at least 20 to 25 minutes holding on then being disconnected). Eventually, I spoke to Miki and explained the that I wanted my son's contracted terminated and the number to be kept as pre-paid. she said it will take 24hrs and will lose the airtime. on the 2nd March airtime was allocated to his number so he went to the store and was told the contract was not terminated. I have since been trying to contact MTN but have been continuously disconnected. eventually on the 4th of March I spoke to Mapasaka and said she was unable to transfer to the cancellation dept as they were about to leave and will get them to call me, to date nobody has contacted me.I even emailed customer service. p.s. ihave have been calling 808 from my cell number and 27()83-1-808 does not work all I want is to cancel my son's contract.