Contract was never cancelled -Router

<p>Vodacom phoned me for a contract for a router with cheaper data every month. I was unhappy about my contract upgrade so when I got the new router I send it back in its orignal packaging a day later. I heard that Mondo does the cancelation so I spoke to a person who cancelled it for me even gave her a good review on hello peter only to found out 3months later Im responsible for R3000 worth of data I used which Vodacom try to deduct from my account in April till today Vodacom holds me liable for something I didnt take and want ro put me on Itc please explain how this happend</p>