Unlock my device from your network

Been trying to get hold of call centre for so I can get them to help with security code. No one there except for Tobi system. I tried using the USSD provide but the their system says my device is not registered with them Vodacom please unlock my device for a 12 month agreement is finished. I want to use other networks please. I've been trying to get through to your call centre agents for the past 3 months and I only get answering machine.