I paid for a line I asked to be cancelled

On 27 January 2015 I asked whether I could upgrade my cell phone contract I asked the consultant to cancel the my mtn tablet line of R325 for *** . I upgraded my *** to an iPhone 6 . End of March MTN deducted R933.99 which is the R325 for my tablet ***) R 499 ( I phone 6 my upgrade) when I went into the Parow centre branch on 1 April I was told that even though they cancelled it from their side It was my responsibility to ensure its done ,and I was told that I must call the call centre myself and cancel the line. Why is it my responsibility if I asked the consultant when I upgraded my contract to do that? I don't get through to the call centre it just ring can some assist me to cancel this line .because of a consultant not doing their job I had to pay an extra R434.99 which is unfair the mtn call centre is unreachable