My account debited but i do not have their device.

I was intending renew my account wit vodacom. Device was delivered and it was not what i asked for. I called that they fetch the device. They took about 2 weeks to collect and told me i cant cancel the contract whilst the device is with me. They then fetched the device. I called to cancel the contract. My account was debited an amount of R279 this month. I called them to enquire and asked them to return my money. That was not done. I called again they said they will get back to me. I haven't heard from them to date. Can you kindly please assist me with this as i cannot be paying for something i dont have.