change of banking details

I went to cell c in sandton to upgrade one of my contract and to cancel the other one only to find out that I m unable to do so because the account I wanted to cancel hasn't been debited for few months and that I have to pay about R278 . What I fail to understand is that I changed my banking from FNB to Capitec months ago and the consultant that assisted me only update one account so they have been debiting the FNB account which is closed. <br> Cell C wil not take responsibility for their mistake they expect me to pay them this money even though its the mistake on their part.<br> I shouldn't be held liable for this because I went to the same store to update my banking details and the updated one account not both of them. How is that my fault? Both accounts are less that R100 so I do not a notification from the bank.<br> I feel that this is not fair and Cell C must take responsibility for their mistake.