Cancellation of landline not done

We sent though cancellation forms on the 27th of May to cancel our landline for a house that was sold. The new occupants are now moving in and will be able to use our phone as it is still not cancelled. I request a refund for our line rental and should any costs occur when the new occupants move in we will not take responsibility for it and will not pay for it. Telkom will bare all costs incurred from not acting on the cancellation in time.