Incorrect billing

I did an upgrade in August, the phone was delivered on the on the 20th of August 2018. I was not happy with the phone and called the next day on the 21st of August 2018 to arrange for a collection ref CCD286188. I was told RAM would come and collect. the phone was collected and was advised someone will get back to me within 72 hours. I waited patiently with no feedback or response i followed up. i cant remember who i spoke to and was told the cancellation was done REF ********** 046. No feedback , I CALLED AGAIN on the 20th of September and was given this reference ********** 536. I had been assured this was cancelled, then my account was incorrectly billed with an amount of R544.88. I called to inquire about the amount debited no one could assist. i have made more than 8 calls and no one is willing to assist or explain the overcharge. may someone kindly get back to me ASAP.