UNABLE TO REACH CALL CENTRE

We have 4 lines with MTN SP and are trying since December 2014 to cancel the data line. We went to 2 stores and both of them told us it can only be done by dialing 808. When u dial the number the IVR comes up then a beep and then the line is disconnected. We went back to the one store and they tried to phone the Dealer Helpdesk, but after holding on for more than 60 min, we left the store. The retention dept is unreachable, even by their own stores. We are so frustrated, because the debit orders goes off each month but we are unable to cancel this line. You cannot email of fax them it needs to be done by dialing 808. Whilst we were in the store the last time, another customer came in and complained about the exact same thing. It does not help in telling the customer to phone 808 - you simply cannot get thru to someone. We don't know how else to get this line cancelled - please assists Account number A*** line to be cancelled ***