i cant ge t ahold of the their call centre

I have been trying for the past three days to get through to mtn to cancel terminate one of my contract, emailed them twice all they did was to acknowledge receipt of my email and they doing nothing in turn.. Even this hour im told all their consultant are currently busy having been holding for 11 minutes.,i need to cancel this contract***),if im billed on it for next month I will accelerate this.