Contract cancellation

I've been calling customer care for the past week and no one seems to be able to help me with cancelling my contract with has reached its full term - I get calls EVERY SINGLE DAY asking me to upgrade. I've been routed to billing department/retentions department - NO ONE seems to know how to log a cancellation request. I've spoken to Emihle Ngcuka (*********** agent), a Buhle - lots more & NO ONE seems to know cancellation process!