Treated unfairly

On 11/10/2014 I phoned DSTV to indicate that I wanted to cancel my account from 1/2/ 2015. I was advised to phone end Dec to give one month's notice, which I did. I requested to stop my debit order 3 Jan, after my last payment for the month of Jan, which was processed. I was advised to phone end Jan to cancel the service, which I did. I phoned twice, the second time to make sure it had been cancelled. I did not hear from DSTV again. To my surprise, I received a phone call from a debt collector today querying R529.17 that I supposedly owe DSTV?! I immediately phoned the call centre, which left me feeling utterly let down, frustrated and accused. I was told that DSTV has no record of the phone calls I made end Jan 2015, and the account had not been cancelled! I moved out of my premises 1 Feb, and did not have access to a product that I have been charged for. I would like an explanation for the following: 1. Why were the phone calls not documented? 2. The contract is month to month