Vodacom doesn't want me to cancel my cell phone contract with them

Vodacom doesn't want me to cancel my cell phone contract with them. First when I called, the operator who assisted me made hold the line until I was frustrated, she then took my ID number and cell phone number then promised to come back to me, which never happened. I tried to call them back again, but no is taking my calls, since I'm using a different network to call them, I'm just wasting my airtime.