Dispute number ***2: Unfair service charge

I sent a request on 21 Jan for cancellation of my telkom account on 21 Feb and immediately received an acknowledgement of receipt of the email. The line was subsequently cancelled on 18 Feb. Now I have recieved an account with a service charge for the full month service fee (R428.07) which they classified as a notice fee (kennisgewingskoste). This is unacceptable as I have given the full month notice they required, in writing and received acknowledgement of receipt of the notice. I have lodged a dispute with Telkom which was subsequently rejected, with absolutely no clarification on the reason for the rejection.