Phone returned to vodacom- still being billed for it

I order an I phone 8 online from Vodacom. Received it on 3rd July 2018 delivery by RAM.

Vodacom allocated a wrong cellphone number and I requested for them to collect the device which they did . however the contract was not cancelled as requested. RAM collected it on the 13th July 2018.

I have phoned Vodacom for over 3 weeks. Initially they confirmed receipt back of the phone. Now the story has changed. Now they say they did not receive the device from RAM.

I want to cancel my contract.

Vodacom is billing me now and debiting my account for the phone that is not even with me.