DEFAMATION CASE AGAINST CELLC

I cancelled my contract with CellC over 2 years ago, but it still recurrs on my monthly credit score as an outstanding charge.

Is that even legal? To cancel a contract but the other contracting party doesn't cancel even after a formal request is rendered. This was not a lifetime contract, it was a service contract, which could be cancelled by either party at any time.

I think a further read into this would serve me well before opening a case of defamation of character, because their unwillingness to cancel the contract is portraying me as the guilty party.