no answer at call centres

Im trying to get hold of customer care on 808 to cancel my contract with mtn as my 24 months has past and i no longer want to make use of this bad service. I just simply cant get through. There is no answer. I can phone 4 times a day and hold the line for 30 min but still nothing. If i go in store they tell me they cant help i need to phone 808. This means i cant cancel my contract and will have to pay for an extra month. I work in a call centre environment and cant be on my phone. So when i phone lunch times tea times and after work i expect atleast once my phone call should be answered but no.