Vodacom Contract

I would like Express my dissatisfaction with Vodacom. They are refusing to cancel my contract at the end of this month when my contract ends. They had sent me a new phone last year Jan without my consent and i returned it the same day. They acknowledged that they receive it last year February. Now they are insisting that i should pay for the phone whist i dont and it was sent back to them. I am a pensioner and cannot afford to be exploited by Vodacom. I went the branch and they were unable to assist saying that i should call the call center. I called the call centre and they are sending me from one agent to another. I need assistance.