Unable to cancel unwanted contract for 4 months

I was contacted by the vodacom contacted by the vodacom contact centre claiming that I had won two mobile phones from vodacom in July 2017.

The phones were delivered and I signed for them. When I realised that I had in fact been roped into an additional contract, on top of the one that I already have with vodacom, I tried calling to get them to cancel it to no avail.

I keep on being sent from pillar to post every time I called, and when I go to a vodacom outlet they tell me that they can not assist, and I must call ********** , which I have been doing for the past 3 months.

I have not used any of the phones, nor have I made or received any calls on them.

I have had money being debited from my account every month for this contract, which I can not stop at my bank, because it's linked to my original contract which I use for business purposes.

I am 71yrs old, and I feel taken advantage of and all of this stress is beginning to take a toll on my health.

Especially something that I never asked for.