Vodacom s ********* business practice

I took a contract with Vodacom in 2016. A device was delivered to me but I called the following day to cancel and a driver was despatched to come fetch the phone. To my surprise I was billed for 5 months and cancelled. Call ccentre agents promised I would be refunded but to my surprise I have since been receiving calls from Vodacom s collections and their lawyers to pay the account. I refuse to pay and I 've been saying Vodacom owes nmw instead.